I have had a breakin in my car, and alot of wiring were cut. Now the car atleast starts, windows work again, and doorlocks work. But stereo isnt cvonnected yet. On the back of the stock stereo I see antenna, a power plug ( I assume), and a place where there seem to go a long larger connector. But I'm not sure if thats so. Is it supposed to be one big connector in this area, or three small ones as pictured?

87 will have 3 4-wire connectors and one 2 wire. I can't seem to pull it up at the moment, but I know there are a couple of posts in the stereo section of this board where I reposted a couple of wiring diagrams for the harnesses.

now, I don't know what direction you're looking to go for future stereo stuff, but I've got the same wiring harness as you and opted to change it over the the newer gm harness style. Since I wanted to use a basic GM cd player, this gave me more plug and play options to chose from. food for thought.

and sorry to hear about the break-in. I've been there before.