>>384793090
Most of the time the underwear is just the body mesh that's been cut appropriately and then thickened a bit, so it should be easy to remove the body mesh underneath and re-join the rest of the body and underwear.
You could also make a copy of the body mesh, then bake the texture for the body+underwear to a new body mesh so that the combined texture is transferred.
Either way should give you a nice exposure to different tools used in blender.