A solution for Master_America, the SCM Toolkit can change an existing maps tile set to another tile set, with one click.
I will admit, it's not perfect, it has a tendancy to swap map doodads, like trees, for rocks, and tar for ice.
But, at least the triggers and locations move over whithout a hitch, and you have the new tile set, without having to start over from scratch.
You can always go in and edit appropriately with SCEditor.
I know for sure this works, because I took a "Turret D" map, and converted it to Desert, and Ice.
Ten minates of cleanup, and it looks like a new creation, and yes I left full credit to it's original creator.
Same with a few of my melee maps, click, edit, done.