How to fix a game controller?

Hi there

A few days back I bought a super nintendo, a controller came with it and a free one was thrown in because the clerk wasn't sure if it worked.

Lucky it seemed fine, all the buttons work perfectly but the left button the D-pad is broken

*(To clarify it does work but it's not very responsive, it's not jammed in anyway so grease wont help) Anyway I heard I should take it apart and dust it throughly. Only problem is i'm afraid to break it. Does anybody have an easier solution?