a. You can actually ship your motorcycle in your household goods!! Lots of folks bring their motorcycles over, or buy them here and ship back. Just be prepared to buy full leathers once you hit Europe. Safest thing to be wearing when you are flying down the Autostrata at speeds of 130 kph +.
b. Yep... there are always cars up for sale on the Lemon lot, and there is new car sales on base. If it is American spec.. no issues about shipping it back. You are authorized one POV shipment on the USAF. Now, if it is Italian spec... not sure of the rules. I know for UK spec the rules are very tough and can cost quite a bit in import charges. You would have to research that one when you get there.