I replaced the rocker panel end only. What I did was clean off the paint where the spot welds would be. Then took a grinding wheel and grinded through the metal till the weld broke, and that way I didn't put a hole in the bottom metal. After everything was off I cleaned up everything to test fit it. It is very important you have the door on when fitting it so the gaps look good. Put some weld-thru primer on it and weld it up. Oh I added por-15 under the panel before I welded it back up. The grey stuff is por 15, and gold is weld thru primer.
I hope this helps somehow.