I would encourage you to keep looking on craigslist. Ask your friend if you can ride the Fuji and see if it fits.
First some things to consider is your height is going to make it more difficult to find a bike and fit is the most important thing to consider on the bike. If the Fugi fits see if you can barrow it for a couple days to see if fits your needs. Also, go to the local bike store (LBS) and test ride some bikes, MTB, hybrids, and road bikes. See how each feels.
For a five mile commute any bike will work. You may want a bike that can take a rack so you can carry your books on it. At your weight I would trust any MTB and most road bikes.
Hey, if you aren't too picky here's one to look at
http://wichita.craigslist.org/bik/1075532498.html the green one. Has fenders, looks like a large size and a rack. The upright hybrid riding position, get you started.......or NOT.
I think you should be able to find a good used bike in your price range. Some may mention to go to a LBS for your first bike to get fitted correctly. I think if you test ride some bikes and then find a used one you feel comfortable on you can tweak it to fit correctly.
Once you ride for awhile you will have a better feel for what you want in a bike and then can upgrade if you desire.