Repairing iPod? (Apple.com Support)

I have an old 20GB 4G iPod, not color. I get a folder and exclamation mark, restore and reset does not fix it. I've tried just about anything.
A few questions about this:

1. How much does it cost?
2. Do I need a warranty to use this service?

Also.. if you have any suggestions to fixing this, it's all welcome!

Thanks in advance!
Lurk