If humans returned to the original Apollo landing sites, what previously left-behind equipment could reasonably be salvaged as part of a future mission or colony? That is, is everything that was left behind in the 60's and 70's essentially junk as of 2019, or are there individual parts or even components that are likely to be still functional or at least capable of being repaired by astronauts on-site?
In response to @called2voyage's comment, I am primarily asking about the technical side - that is, if we assume that it is NASA that is returning, or an agency that has obtained permission from NASA to salvage its stuff, and especially asking about cost-effectiveness - that is, is there anything where it is likely to be more cost effective to salvage the one that Apollo astronauts left behind than to ship a new one from Earth?