Open iTunes > Help > iTunes Help
In Contents > Expand The iTunes Store > Select Managing Your iTunes Store Account.
You'll see the following topics which should answer your questions.
If you want to move the contents of the ipod onto the PC you'll need to buy a third party program. Use Google to find one on the internet.
- Managing your iTunes Store account
- Setting up an iTunes Store account
- Signing in or out of the iTunes Store
- Changing your iTunes Store account information
- Authorizing a computer to play iTunes Store purchases
- Viewing your purchase history
- Making sure you have all your iTunes Store purchases
- Moving your iTunes Store purchases to another computer
- Using iTunes behind an Internet firewall
Thanks to xpcman
for this tip on the forum.