used to drive a manual IS300. great car btw

so im in the market for a used bike but im really scared that i'll buy a lemon! i have a few questions.
1. is it possible to turn the odometer? i know it must be impossible for the digital ones but how about the analog ones?
2. how do i tell if theres something wrong with the engine??
3. what kind of mileage is considered to be alot and little? im assuming these bikes will have different life spans compared to cars?
4. do you recommend any bikes for me? im looking for a quick, nice sounding bike either race or cruiser style
thanks