1. Same bolt pattern. They will fit and not rub.
2. If they're the ones that I'm thinking of, yes I'm 99% sure. No problem switching to 195/50, although your speedo will read high and you'll have slightly shorter effective gearing.
3. Yes.
4. Yes. Your mechanic is as much of a tool as the ones he uses on the job.

Kinda like the mechanic who told me that "lowering the car will ruin the handling."
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'98 Integra LS - non-VTEC autocross / daily driver (aka Track-Tested / Mother Approved)
Daily-driven 87 octane Porsche destroyer
Latest Auto-X: 5th overall in class (7th/12 Day 1, 2nd Day 2). 10th/92 overall Day 2.
Complete mod list and updated race results here:
http://www.freewebs.com/white98ls - don't forget to sign the guestbook!

Autocrossing for a day is the best $25 you can spend