I think an overnight soak in hot PBW and a starsan soak will take care of anything on the stainless, just replace the gaskets and poppets if you are concerned.
I would definitely recommend keeping the kegs though, they seem to be rising in cost, so if you ever need more in the future, you'd have to pay more to get them then. I have 90 kegs, and am still looking for more.
Walk-In Serving(14): Oatmeal Stout, Hard Cider, Belgian Tripel, Liquid Stupid, Belgian Dark Strong, Red Bull, Rye IPA, Double IPA, Imperial Stout, Irish Red, Scottish 70/-, Belgian Wit, Nut Brown, Traditional Mead
Walk-In Cold Storage(~50): Cysers, Braggot, Melomels, Ciders, Traditional Meads, Persimmon wines, Dry Stout, barleywine, cream ale, sodas, Chocolate stout, milk stout, and others I can't recall.
Fermenters (0): Nothing current.