bad news man, thats got to suck!
and in answer to your questions,
1. no on the coilovers
2. Power FC's can be hidden, but best to put in a standard ECU.
3. best to borrow a standard exhaust.
4. 18's are legal, depends on offset, best to borrow stockies
5. diff should be ok, as long as they dont hear it makin noise, or your tyres chirping when you turn.