There are some very good tutorials and instruction sites online. I'd probably buy it, negotiate the price since it's not working and take it home and play with it until I could get it sewing.
One easy fix, is to clear any thread that is stuck around the bobbin case. I've seen three machines now where there was so much thread in there that I'm surprised it could move at all.
These little machines are really easy to open up and clean, so don't let a "won't sew" slow you down. :)