bc,
Try turning the volume control its full travel about 50 times. This might clean it up. If you open the amp up, it is very hard to spray it with contact cleaner as the holes face the circuit board.
For packaging I would use 1 layer of bubble wrap and double box it.
For the inner box you can actually make it from a bigger box – unless you are lucky enough to find two boxes the correct size. I usually add two pieces of cardboard over the cabinet front. Using double boxes is a good idea if you intend to get extra insurance over the standard $100, because if you get the extra insurance they will usually open your package to see how well it is packed.
-LesS