Howdy, neighbor. If I understand your question, when you set up your 3G iPad, instead of setting it up as a new iPad, restore a backup from your Wi-Fi model. This will place all your apps, media content, and settings onto your new iPad.
Greg, what have you decided to do with your Wi-Fi when you migrate to the 3G? Sell it? Gift it to another family member? I'm trying to decide my best approach...
I am debating about this at the moment as well.
One thing I want to do is to return mine Wifi version and exchange for a 3G version. The return date on mine is 17th, and I guess this goes with everybody else.