What you are proposing should work just fine. But if you do make a mistake and mess up your grub, don't panic. Grub can usually be fixed without much difficulty. No need to reinstall because of a messed up grub. Just come back and ask and someone will be glad to help you.
If you have access to only the one computer, you can use the Mint live cd to return. Or, you can download a small fast live cd like Puppy Linux to use as a back up. The beauty of that is that it runs completely in ram, is fast, and doesn't need the hard drive or cd drive once loaded. I use Puppy shard 3.01 as a backup and tool kit. It is only 155MB.http://tmxxine.com/Wikka/wikka.php?wakk ... xxineShard