I wouldn't worry about the rearend too much. If you can rebuild the rearend yourselft then great, but I'd go ahead and plan on spending $500 to have someone replace the gears and most of the other components.
Check for oil leaks the best you can. If that engine really is bone stock and has 200,000 miles, I would consider the engine in the price. Instead, is the rest of the car worth $3,000.00? You may get another 20-50K miles out of the engine, but that is a lot of miles SOMEONE ELSE has put on the car.
That may be a good price if the body is in great shape with little or no dings and only a few scratches. The interior should be pretty clean, too. Hopefully, all of the electical stuff works and it appears to be a solid car.
If I were buying that car or even my own, I'd be considering a new/rebuilt engine, rebuilt tranny, rebuilt rearend, and a total suspension upgrade/replacement (springs/shocks/struts/braces). In the end, it is cheaper than buying a new car AND a rebuilt/new engine could result in over 300hp with the right mods.
Oh yeah, you might want to replace those brakes, too.
Sounds like I'm saying you're going to have to replace everything, but when buying a 200,000 mile car........is there really any reason not to expect that you're going to mod it fairly well? Stuff will go wrong eventually, depending on your driving habits and the level of care taken by the previous owner(s). 200,000 miles on a stock engine probably means the owner(s) have done something right in taking car of the car, so don't take this as being too negative.
Good luck.
