Welcome I'm in the same spot I bought a 2003 4runner 150k 2nd owner and no rust in the undercarriage it was brought from new Mexico area clean engine bay I'm happier than a new 2021 car owner these engines are build like tanks god bless your car man hope it last for 500k miles!
Might want to use a auto motive light sand paper to see of that clears the stain of top of the plastic or even simple green is good but that looks like a water stain from something acidic that trash bag holder seem like a good way to mood it into a table for the back passengers instead of a...
