When I went into the pits, there was a whole lot of stuff in there hardware wise, but I was the only car, so I didn't notice any other mechanics. If I'm correct, I think that the pitcrew mechanic sequence is kind of an FMV sequence where the car is changed depending on what you're driving. I know that isn't really possible but you get what I mean right?
Yes, cars come with a certain amount of mileage on the clock. My Evo had 45,000 km already. The lowest milaege cars have 10.0 km on them and they are priced at original value.