This is very true, about "opening a can of worms" (regarding rust).. I just replaced the rockers on both sides, and before starting, i told myself, this would be easy and fairly inexpensive (and i do all the work myself).. however, after removing the rocker, i found that i needed to replace the inner rocker AND front doorpost... along w/ floor boards kick panel, and inner fender apron... finished the drivers side (ALL new), then went to the passenger side, removed rocker........and it was identical to the first side... Just to let you know.. Door post ($159), Inner Rocker ($39.00 ea.), Kick Panel ($60 ea), Inner Fender Apron ($50 ea)...Rocker panel ($70 ea)... so ur looking at around $380-$400 per side, just in sheet metal, if you do it right.. That would not include paying someone to weld it, fit it, and prep it and seal it... I did all the work myself and still cost around 800 for both sides.. Hopefully your's is not as bad as mine was, but, now it's all brand new and good for another 40 years.. Good LUCK!!
Luke