1989 Riviera Radio Woes

When I am at stoplights or slowly cruising, my radio (CRT) does what I have seen on here a few times called hissing and snapping and crackling. Once I get a comfortable speed going it kinda slows down sometimes.:banghead:

I am pretty sure from reading the other posts that it is the amplifier or resistors in it. My question would be:

First, is it only one, or are they located on all of the speakers?

Where is it located and how hard is it to get out?