If you have Halo 3 Mythic Disc, is it necessary to delete the map packs you have already downloaded?

Alright, I recently bought Halo 3: ODST, and with it, came the Mythic Disc. I have already downloaded all content but the Mythic Map Pack 2, but I have just been wondering if you needed to delete the map packs already downloaded, or it might mess up? Are there any errors if you have the maps downloaded buy prescription drugs online and you play on the Mythic Disc? Thanks, Raven.