I just did the rockers and cab corners on my buddy’s 06 duramax king cab. The inner rockers are usually bad too. We buy everything from fixmyrust.com. They have some nice thick sheet metal. The company that makes them is Key parts I believe. We cut out and welded in all new inner and outer rockers and cab corners, expoxy primed everything, then shot it in black bedliner up to the bottom body line. We sprayed the bottom of the bed and tailgate too. It turned out pretty good. I would guess you will be in the $2,000 price range to pay someone to do it. That includes all materials.