It's kinda like saving before opening a chest, opening the chest, then reloading till you find something you like. Once it's created and burned in (saved) nothing will "uncreate" it. I'm afraid you'll have to start over for BFII, but I'm afraid if you're Lv. 8+ the dungeon won't be much of a reward to you. I hit the dungeon at Lv. 10 (and that's the moment I got to the barracks) and mowed through the entire dungeon in 2 minutes.