There is a book that tells you how to maintain your own Featherweight. I can't think of the title right now but someone else may know.
I can't give you much advice on buying other than that I won my first in an Ebay auction and was very pleased with its condition. If you went through Paypal and wasn't happy, I think there'd be a way to take care of that but others may know that as well.
Do you have Craigslist in your area? That might be an option too but please be safe about meeting up with strangers.
Good luck,
lots2do