thank you, everyone! i got q-tips and white vinegar, laid down a big piece of thin cardboard that had been a shipping box or something to throw away, got some cheap blue disposable gloves (nitrite?), and cleaned the inside of the battery compartment. i used the white vinegar very liberally. it did fizz up and dissolve the caked-on crystals of battery reagent!
i tried it with (admittedly old-ish) batteries and the motor moved for just a second, and then died. i then tried it with newer batteries and it didn’t move at all. so it must have other problems. new quest lol?
again, thanks to all who’ve contributed!