When their nails start to seem a little long trim them with dog nail clippers.

Do you feed them fruits and vegetables? If you do, start feeding it from your hand. It will just take patience.

Check out these sites:

www.cavyspirit.com
www.cavycages.com'

And search 'cavy care' or 'guinea pig care' in google and you should find more sites. If you need anymore help, PM me.