Problem with RX-V870; I am clueless.

Just bought an RX-V870 on Craigslist. Price was okayish (no remote, but I already have one) and it is in good cosmetic condition, but ...

Two problems:

1. The display light is out, which I am not concerned about (I understand that this is an easy, quick, and inexpensive fix); however,

2. When I turn the receiver on, and the speaker protection relay clicks a second or two later, there is no sound at first, and then the sound slowly (over the course of five/ten seconds maybe) comes up to volume, but it is very, very distorted ('fuzzy') at first. It seems to go away in a short while, but I only have some second tier stuff to listen to it right now, so I can't say for sure that it does sound the way it's supposed to.

I do not own a multimeter (never even held one in my life), and wouldn't know what to do with one if I did, so I'm not sure I'm going to benefit from advice significantly more technical than "take off the cover, pull off the big blue thing, and replace it with part number such and such from PartsExpress."

I'm hoping this might be some common problem with these receivers, much like the light thing.

Thanking you in advance, I am your most humble servant, MisterMousePotato

By some odd coincidence, yesterday, while digging through my host's belongings in search of an oil filter wrench, I happened upon a multimeter, so it is no longer true that I have never held one. From my inspection of it, I gather this is a device designed to measure electricity, but that's about as far as I got. It refuses to give up its secrets.

Am I now sufficiently equipped to diagnose this problem?

Any help (even a kind word of discouragement) would be greatly appreciated. Thank you.