In terms of getting all your contacts / photos sort of info onto the new device, if you are currently syncing successfuly with iTunes, then you should be pretty set - iTunes should sync all across to your new one - though it is always going to be worth confirming this of course.
As for wiping your data from the old one, depends on what your deadline is for selling. If possible, it might be worth waiting for the iPhone 2.0 software update to come out (by 7/11) as it will include an ability to securely wipe all data, which the current software does not. So if you want / need a truly secure wipe on existing software, it requires jailbreak and a lot more manual labor than it will on 2.0 ...
It's going to my daughter so security is not such an issue and giving her a clean device to start with. Our taste in music is way different - she's a little bit country and I'm a little bit rock & roll
How will my iTunes account know that the old Ipod info should go to the new Ipod?