Good to hear you got it already and installed too, boy you don't mess around!! It was 5.85 for the shipping and the little cardboard envelope was around 2.50 (I can't remember for sure). As I said earlier don't worry about it, but if you insist on paying the shipping $8 will cover it good enough. I'll PM ya.
As for the power top motor, sounds like you got it cased. Likely could get away with 12 ga. but as I said before these things draw a lot of Amps and its cheap insurance. I did a relay set up right at the motor as I didn't want to rewire the whole thing. Thats why I ran the power to the back. For what you are doing it will work 100%. Also try to use a battery charger or run the engine when putting the top up & down to maximize voltage to the motor.