If you buy 4' fixtures, some hooks and some light chain, it all comes down in minutes. Install pigtail cords long enough to connect to a switched box. Most of the time it is OK to run romex above 8' and along rafters, not on top. Coming down the wall it must be protected or in conduit. You can wire up the place in a few hours.
Just bear in mind that you probably have only one circuit to the garage for a light and maybe an opener. If absolutely no power out there, you will have to do a home run back to the panel. It's not a good idea to tap into the closest circuit except for bare minimum lighting.
Post over on the Electrical forum for more info.