well i jus broke my arm at a soccer game so i cant do anything right now and for like 6 weeks (no cod for 6 weeks and blackops is coming out soon oh and will alter iw come out with something for blackops like mw2)
Ok start the the hack, then start the game, don't go off the menu.
Now switch back to the hack and apply whatever level and prestige you want.
Now go back to the game and play maybe like a small round.
Then quit the game and the hack.
Now start the game with or without the hack whatever you want.
Anyways, it should be saved and you don't have to do the level/prestige hack again.