Re: motor kit suggestions
I like the way you think. Since this is your first build, keep it simple. You don't need a shift kit. The 80 motor already goes faster than is safe. Don't expect to cruise faster than 35 mph. That's about the upper limit of safety, and reliability.
Be sure and check the laws in your state about motorized bicycles before you waste a lot of time, and money only to find out they won't let you ride it on the street.
I would advise getting a SkyHawk, or Flying Horse motor for a first build. They're less crappy than a lot of the other brands, but not by much. Don't expect much warranty, and you won't be disappointed. Do strip the motor at the very least down to the block. Expect to find a few things needing minor attention like seals, or gears not properly installed.
Expect some teething problems at first. It takes a while to get all the bugs worked out, especially on your first build. After that you'll be able to ride to work everyday and get over 100 mpg doing it.
There's going to be some extra accessories and hardware you'll need in addition to the kit parts. Although you can build a motorized bicycle for as little $350, for a good dependable motorized bicycle expect to spend $600 to $1000 before you're through.