Have you taken the electrics out and had a look at them ?

It is very easy to switch out and replace pots with new ones if they are not working or crackling.

I recently did this to a strat volume pot (as well as shielding the internal cavity).

Have you checked out stewmac.com ?

They also do a video describing the workings of either a Fender or Gibson type guitar (they are about 10 bucks each). They are very good for people who have never done this type of repair before and a refresher for old hands that think they may be a little rusty.

This thread may also be useful:

http://www.guitartricks.com/forum/showthread.php?threadid=4727