Welcome to the forums! I hope you enjoy your time here! There is a LOT of information here, the search tool will help you a lot!
I can try to answer some parts of your questions
- Power: Probably the best power supply is the Opus - search here for Opus!
- Wiring: Use the standard places the factory wiring goes - pillars, under carpet etc
- Upholstery: Most stuff in newer cars is either clipped or screwed in. If needbe, go to your local dealer and ask the best way to get x bit of trim off.
- Line noise: Try to keep all your audio cables away from power cables. Also, try to ground your audio equipment to the same point. Use reasonable quality cables - especially for grounding, which is just as important as providing +ve voltage! Also search here for "ground loop".
- Basic acoustics: Go to your local car audio specialists, and ask them specific questions about your car. They should be able to tell you which combinations of equipment will sound good together.