Hey- I don't regularly check this site, so sorry for not responding earlier. Anyway, the "buzzing" fix is fairly easy. The C52 capacitor (location on the pcb, not a model number or rating) is located just above the two large smoothing caps on the amp.
First you need to locate a 47uF 100v 105degree radial capacitor. The one that has failed is a 63v 47uf 85degree one, but you need to "upgrade". I didn't have any place nearby that sold them, so I bought two from ebay. They cost $2 shipped.
Second, you need to take out the plate amp from the box, remove all the wire connectors connecting the amplifier part to the pre-amp part (the amplifier itself is the pcb that has the two large caps attached, and the transistors that are connected to the large heat sink.), and then unscrew the amp from the back plate.
I found that I was able to unsolder the C52 cap from the amp pcb without disassembling any more than this. If you're not able to access the posts underneath, then you'll need to unscrew the pcb from the bracket as well as unscrew the transistors from the heat sink. My advice is try first before going through this extra work. Make sure you note the polarity of the cap before removing it, and install the new one in the same orientation. Once the new cap is in, you just need to reassemble everything and plug it in.