Are you removing the entire thing, or just the outer rusted lip? On my car I only had to remove about 2-3 inches of the outer wheel well lip. I cut the good one up, fitted it over the old one, marked a line, cut if off with a die grinder and tacked the new one in place. I then went back and carefully moved around tacking on it until is was a solid weld, being careful to skip around and not warp the metal. Once I was done I ground it down with some cutting wheels, cleaned it up good and seam sealed it. If you are going more indepth that this, you might want to do a search, as this has been discussed on here a few times...you might find what you are looking for in a past post.