Originally Posted by
a1penguin
Ick. That looks horribly rusty. Replacing the mechanical parts alone (cassette, derailleur cage) would be more than the bike is worth :-/ They should freecycle/recycle/donate that bike. It's just wasting space. If you can get the Expedition in ridable condition with elbow grease, it might be worth a try. Or sell it and put the $ toward a new bike.
First locate a bicycle co-op within your community. If such a thing exists, then continue reading...
I would disassemble that bike and inspect it thoroughly. If there's just surface rust, then sand the rust off manually and treat the remainder rust chemically. I'd use those round wire brushes (what they use to clean gun barrels with) to clear the rust inside of my tubes. If there's much rust internally, forget it!
Take many pictures of your bike, before disassembly, at various angles. As you disassemble your bike, take a picture or two with each step. Take a picture of the disassmbled part plus the frame. Label them as a part in the step. Then thoroughly sand your bicycle inside and out. Clean all sanded particles off your frame with denatured alcohol. Have your frame powdercoat painted. Treat your frame's tubes, internally with JP Weigle's framesaver. Take your frame and salvaged parts to the co-op. Join the co-op, by becoming a member.
* Perhaps you could sand the rust off of components, as well...
Whatever, parts you couldn't salvage, look for them in bins at the co-op. They might have components that fit. Whatever the co-op doesn't have, you can find on eBay or at your LBS.
Good Luck!
PS.
Of course, it might be less money and most certainly less work, just to purchase online with bikesdirect!