jaksen112,
Should be pretty simple procedure.
If you have MF XP running, all your licenses are stored in the Datastore.
You would simply install 2k or 2k3 server, install MF and all your apps. Then add those new servers to the load balanced application and you are done. Nothing will change.
I've done this going from HP DL360's to IBM x335 series servers.
Hope that helps!