[Tusker]

I would use a torch to get the bolts apart. Heat them cherry red and walla.

For the cat, Petroworks sells a replacement one for $89. If you want to do the entire system, Traitough has an entire system in 2" for $329 that you could easily install yourself.

 

[Tusker]

By torch I am assuming you are refering to a welding torch?

All you need is a bottle of MAP gas (looks like the small propane bottles except the bottle is yellow instead of blue) and a decent "torch" tip and you are in business. Probably cost you $50 or less at a good hardware store.