You'll need a pry bar for rubber hangers, a metric socket set. An o2 sensor socket if your car is OBD-II (has 2 o2 sensors)

If you're buying a cat-back, that's the only reason to be concerned with the rustiness of the bolts. Otherwise, if you're doing the downpipe or "A" pipe back (from the manifold) including the cat, it will be super-easy. Air tools or a big breaker bar will easily rip the manifold nuts holding it on right off, and you can drop the whole exhaust at once without mucking with the rest of those bolts. Use PB blaster on the hangers and bolts/nuts for a few days and heat cycles before you start taking it loose if you have to, though.

The turbo-back exhaust I bought from Apex'i for my DSM was the best fit I've ever had bolting anything aftermarket to any car. It fit better than a lot of stock stuff I've purchased. It came with everything needed hardware-wise. Gaskets, hangers, etc...