a massive ammount of work and i am a electrical biased, with a understanding knowledge of electronics.
Its all going to be surface mounted SMT leds, which are a pig to change. I know, i changed my old Nokia 8210 to blue leds!
your soldering skills have to be spot on, with a steady hand, and thats only once you have taken it to pieces.
Its also quite possible that blue leds use more power, so it could be that they wont be compatible/ will overload the circuitry that runs them.
Switches and lcds, are also going to be a pain to get apart and or convert.
Its a job you either got to start and totally finish, or not start at all.
if you get half way and hit a problem, or awquard item your stuffed.