So I just got a nano 4G for my mom and of course it doesn't work with foo_dop for foobar. It's okay though since I need to use iTunes anyway to help her when she gets it.

Question is, if I use the iPod with iTunes on my computer, will it be locked to this system or is there no problem when she gets it? And say I just want to use it kind of like a media storage device instead of something synched to a library on a computer; the things I put on it won't get eaten up when she receives it?

If you load it with itunes on your computer, it's locked to your computer. If you use it like a media storage device, it won't play the music. If she syncs it, it'll overwrite anything you put on it.

Guess I'll just load up my spare external with music, then.

If you mean loading the music you want her to have on the external then transfering that music to her Itunes on her computer then downloading from her Itunes account on her computer to her nano, then that will work. I think I did that for one of my family members.