Well, having done this kind of thing many times before I can make a few reccomendations. I've had the best results system wise with Sony and Pioneer.
Fist you gonna need a deck. Couple a good versitle choices would be:
Sony CDX-F5705X. This deck has just about every single basic feature you could want. I don't think Best Buy carries, but order it if ya can. It's a pretty good deck. I don't know what ya wanna spend, but 200 is a good meadian generally.
If you don't wanna soend that much try a
Kenwood KDC-322. Still has a good feature base and you can slap a cd changer on it.
If you feel like showing off, go for a
JVC KD-LH3100 that Best Buy carries, or order a
Sony CDX-F7700. These step in the the fancier range and look a bit sleeker then the others. May have a few features you won't ever use, but you'll be cooler then every one else, and that's what important in car audio. If I remember correctly, all of the decks I mentioned should have a remote with them that can adapt to the cd changer. If not changers generally come with 'em.
CD changers I can't say I profess too much knowledge in. Most systems I put in didn't include these. When you have a set up subs in your trunk at high power, it can tend to be rough on a CD changer in the trunk. Not impossible, but you have to get a pretty good one. Bets Buy doesn't seem to have a huuuge selection, but from outside of that site reasearch, 150 to 200 seemed to be the biggest available selection.
The only other thing I can think of this early in the morning you'll need is a fit kit. Basically a 15 - 20 dollar kit that includes plastic liners that go around the stereo front perimeter to help it fit/blend with the dash of your vehical. Theres usally a Ford Truck or Honda Sedan kind of set that has a dozen fitters in it that takes care of every model of that car type for that brand.
Maybe a wire harness too for the factory wire set to adapt to the stereo hook up. Bascialy your car has a lil plus that goes to all the speakers and power and stuff that just plugs in to the stereo and the factory plug may not for the after market stereo. Cheap piece though.
Probably come back and edit this later, but this is as well as I can think at 8 a.m.