You literally have to cut the head off. There is a knob so you can't cut strait through.
Don't pull or try to peel it, cut so you don't rip it.
If you heat the head up, I used hot water, it'll go on the knob easier.
This particular body is a DML slender which is easy enough to find, the hands are standard rifle grip but they make optional rifle hands. Now to find him pants.