I was able to drive the car for about 75 miles over the weekend, and so far it's running great! I still saw a little bit of water dripping out of the exhaust pipe where the cat pipe bolts to the mid pipe today but I haven't seen any smoke out the exhaust, no coolant loss thus far, steady idle, no overheat. To fix that water drip I'm going to try flipping the gasket between those two pipes. I don't want to declare victory too early but things are looking good! Thanks again to everyone who posted responses, no way I could have done the job without your help. I would say to any novice trying it for the first time that it's actually not too horrible a job if you have the right tools, and you'll save a lot of time if you get all the tools you'll need in advance, like razor blades/sandpaper for cleaning the block, the fuel line disconnect tools, and I was glad to have an angle grinder to use the old head bolts as studs to connect the exhaust manifold to the cat pipe.