When I cleaned up the exhaust ports on my 400's head I prised out the old gaskets only to find a second set of gaskets underneath!
The exhaust gaskets are crushable to form a seal, so you should use new ones each time.
Sump washers in alloy or copper are just plain washers so can be annealed to soften them for re-use. Don't heat them to red hot though, they're not mild steel. Just heat them up and quench in cold water. Dry off and ready to go.