Welcome. That Fox you're about to acquire sounds like a great place to start. If there was one area of the car that had to be bad, I'd want it to be the interior. Some perspective on your questions:
1. Yes. heat them with a torch and hit them with a hammer. You have to hit them hard yet cautiously. I have Corrado seats in one of my Foxes. They're a nice upgrade. They sit a lot lower, almost too low for me. But still well worth it.
2. I've had four Foxes and always ended up running 14s on them with a 185/60. I also like 13s and 15s, though. I'm running BMW e30 bottlecap alloys on one of my Foxes. They have a 35mm offset, which works well on these cars. They're not heavy and you can usually find them easily for cheap.
3. This depends and, also, everyone will give you a different answer. There are some coil over options, which others here can discuss better than I can. If you want a Fox that is still a fun, relatively comfortable street car, but that you can also autocross in street touring consider something like the following: Front Bilstein sport struts, Rear Corrado Bilstein Sport rear; Corrado Neuspeed Race springs; rear sway bar (Addco makes one, so does Black Forest); Max negative camber up front (which isn't much; adjustable via the ball joints); Front toe out 1/16". You can go a lot more radical than this. But this will be a fun set-up for the street too.
There are tons of other options regarding your questions. Just check the FAQ.
And post some pics when you get the car!