With his walking stick, long white hair and thick spectacles from a bygone age, Win Tin embodies the challenge facing the party that has led the campaign for democracy in Myanmar but now needs new blood to secure its future.

The National League for Democracy (NLD) led by Nobel peace laureate Aung San Suu Kyi boycotted what it saw as flawed elections in 2010 that signalled the end of half a century of military rule in the former Burma but it will contest by-elections in April.

Suu Kyi's stature alone should ensure it gains a presence in parliament but the party can only live off its role in the fight for democracy for so long. It badly needs to develop policies and then win over voters who come of age in the new parliamentary era.

Win Tin has a mind as sharp as when he was a journalist challenging the brutal army dictatorship, which earned him 19 years in jail, but the long-time aide to Suu Kyi is 82 years old and many other NLD leaders aren't much younger.

Our party is too old, Win Tin told Reuters, perched on the edge of his chair and leaning on a walking cane for support. No one has suffered oppression like us, but after serving so long in prison, we've been rather disconnected.

We have youth leaders who are over 50 -- one is even a grandfather. But now that there's an opening, our party needs new life, new faces, new blood if we want to survive and make a difference. It's time for us to make way for a new force.

Suu Kyi has taken the leap of faith needed to commit her party to a political system still controlled by the army and its proxies in parliament, a move welcomed by Western countries cautiously renewing ties with the nominally civilian government.

In a landmark visit to Myanmar last week, British Foreign Secretary William Hague told the former junta leaders in charge of the government to ensure the polls were free and fair, making that one of the conditions for lifting sanctions imposed for human rights abuses under the military regime.

SURPRISE REFORMS

To general surprise, since the 2010 election was so carefully arranged to produce a government the former junta wanted, the new leadership moved quickly last year to free some political prisoners, hold peace talks with ethnic rebels, relax media censorship and allow protests and trade unions.

Despite the bad blood between the NLD and the old soldiers who had refused to cede power when the party scored a landslide win in 1990 elections for a constituent assembly, Suu Kyi has given President Thein Sein, himself a former junta general, the benefit of the doubt and agreed to join the system.

She has called for an overhaul of the NLD and wants to recruit women, ethnic minority groups and educated youngsters to strengthen and rejuvenate the party.

There is much work to be done. The party has limited resources and its headquarters are cramped and crumbling. It doesn't even know how many members it has.

Oxford-educated Suu Kyi also needs to win over the sceptics. Her party is far from united on the need to engage with the people who jailed hundreds of its members and chased much of the country's intellectual talent into exile.

There are differences in the party. I personally disagreed with the NLD running for parliament, but she wants to take the initiative and she accepts that without the military's cooperation, political change isn't possible, said Win Tin, who was Myanmar's longest-serving political prisoner

Win Tin is perhaps the only NLD member who would dare to discuss openly the troubles within the party.

Criticism of the Lady, as Suu Kyi is affectionately known, is almost taboo in Myanmar and despite the differences inside the NLD, party votes have almost always been unanimous and in agreement with her views.

Even so, her new direction has drawn mixed reactions. While she has been widely praised for her new-found willingness to compromise, Internet web boards are full of postings by Burmese using pseudonyms criticising her for dealing with what they see as a government of untrustworthy despots.

Undeterred, Suu Kyi has set her sights set on winning a good number of the 48 vacant seats in the 1,158-seat national legislature.

She will be a candidate herself but has said little about what she would do in parliament or whether, as rumoured, she could take a cabinet post or even the vice-presidency.

POLITICAL PAWN?

Many in the pro-democracy camp harbour deep distrust of the new regime and believe she could be walking into a trap, used as a pawn to legitimise a much-derided legislature.

Win Tin says she is well aware the former generals may have ulterior motives but she is willing to gamble.

There's a lot of mistrust, but she said: 'why should we wait?' She sees this as an opening, an opportunity to work for the country. She believes it's worth the risk, he said.

Some of the people the NLD needs to recruit agree with her decision to take part in an imperfect political system and work to change it from the inside.

They say the priority should be to win enough parliamentary seats in the next general election in 2015 to amend a constitution that enshrines the military's political power.

The problem is the government really is still military. They still believe it should have special status and that's dangerous for our future, said 23-year-old law student Ko Htet.

We have to prepare, because the military can take back power at any time. We've seen positive changes recently and we never want to turn back.

Sit Maw, 21, wants to work alongside Suu Kyi but said the party needed to expand and bring in younger, educated Burmese. One hurdle, he said, could be resistance from its older members.

There'll be differences between the old and the new generation, differences in opinions and ideology, but they need educated people, he said.

I believe in engagement, even if there's mistrust. Thein Sein has kept most of his promises so far, but there are no guarantees, so we have to be prepared.

The rifts in the NLD were exposed in the run-up to the 2010 election, when a faction unhappy with the NLD's boycott -- which came after Suu Kyi said she would not dream of taking part -- broke away and formed a new party, the National Democratic Force (NDF), for which they were derided as traitors.

NDF leader Khin Maung Swe welcomed Suu Kyi's decision to run for parliament but warned that her expectations should not be too high, since the assembly lacked a real debating culture and proposing legislation was extremely difficult.

He wants his party to work with Suu Kyi but warned against over-optimism if she gets into parliament and expressed reservations about his old party's ability to change.

She is an inspiration, the people's leader, but they expect too much of her, he told Reuters.

She wants the NLD to change, but I can't really say whether outsiders will be genuinely accepted. There's so much rivalry for the top positions. There'll be a lot of challenges ahead.

(Additional reporting by Aung Hla Tun; Editing by Alan Raybould and Jonathan Thatcher)