I replaced my subframe without removing the fenders, radiator support, or wheelwells. I did remove the hood, valence, and the front bumper/grill assembly. The fenders were plenty rigid and there was zero movement after the subframe was out. I removed the subframe after I had taken out the engine, trans, and front suspension.

I supported the body with two jackstands with three foot 2X4s between the stand and the floor pan. The wood was placed between the outside of the subframe and the body seam at the bottom of the rockers, parallel to the subframe. I also put a jackstand under the radiator support in case somebody decided to sit on it.