The compass and temp sensor will probably already have the wiring and mounting locations in place.

- The compass gets placed under the rear deck where the speakers are. You fold down the seats, and take out the four visible bolts, two next to each latch that helps hold the seat backs up. Then the irritating part, be patient, because while some people pull them out with east, I usually struggle for a good 10 minutes :/ You have to pull out a push-pin type retainer, one on each side, behind the small portions of seat backs that don't fold down. But once you do that, just lift up the ear deck, and you'll see a square of the insulating fiber cut out for the compass.

- The outside temp sensor Is behind the grill, on the plastic panel between the metal front bumper support and the radiator. There should be a wire harness. You can then push it in place, you'll see what I mean.

Definitely try to find someone who has a tuner or a good scanner, dealerships and the such charge way too much for what they're really doing.