IMO the factory stereos are not worth fixing or getting another one. They just don't sound that great, you can do better with something that is aftermarket, plus you can get other features like sat radio or connects for an iPod. Who listens to CDs anymore, anyway... what a hassle.
Anything that is a standard DIN fit will screw right to the factory brackets in her truck. Then you can get a pocket that sits below the fill the rest of the hole in the dash. I used to use Eclipse head units, the nice thing about them is that they plugged right into the factory Toyota harness, no wiring necessary at all. I doubt they are still like that however. At the worst, you'll just have to get an adapter harness, usually cheap at the stereo shops, some will even throw it in on the deal.
Shop for features and what you can afford. I'm happy with my Alpine that I bought a little over a year ago.