I can't comment on easy of installation on stretch bikes, but a lot have done it. I thinkyou'd encounter more difficulties with a wide back wheel.
As for your questions-
1. A multi speed bike makes for slightly easier mounting of the rear drive sprocket, and make the bike easier to pedal when needed.
2. You may have to re-route your brake cables, opt for a dual lever for front and rear brakes on one lever, or even leave them alone and have the clutch and one brake on the same grip.
3. I don't recall anyone having problems with getting burned....i.e. not an issue.
4. You will really only need to pedal to start the bicycle motor. You may want to pedal to assist acceleration, but that overkill in my opinion.
5. Yes, pedal up to 10mph, drop the clutch and off you go. These are just like a motorcycle with a clutch, no gears...yet. You "bump start" them.
To get the most out of your kit- look here. http://motorbicycling.com/f30/bicycl...-care-354.html