The 70cc should give you the little extra torque that you need to get up hill's, and if you gear it right it should be even better. I have a 67.5cc (the so called 80cc) with a 44t sprocket and do just fine up hill's. I have even gone up several mountain's here in Tucson with no problem's.
As far as e-bay, never bought anything from e-bay so dont really know. I have heard good stories and bad stories from e-bay.
But like GodFather say's...STAY AWAY from revolution cycles!!
Driving time for 15km... Depends on your gearing I guess...I have a 20mph speed limit so I really could not tell you. If I got a long way to go, I just be sure I give myself the extra time that I need to get there on time.
With heavy traffic in the city...even with a 20mph limit...I can get to place's faster on my motorized bicycle then my truck...or about the same time..