Trapdoor expansion in A500+ should add as chip, assuming everything else is working correctly, no damage from leaking battery, not using something "weird" like the AdRAM, etc.
Btw, CR2032 won't leak (it's not a Varta), but if it's soldered in you can clip it out and replace with a socketed one (you can get these from AmigaKit, Amazon.com, etc.).