worth the effort? I have a few that look good but are used.
IMHO, once the washer/gasket is crushed, it is compromised. I'd not re-use the washer. If you can get some copper replacement washer/gaskets, you can re-use them after annealing them. (Remove washer and heat it to cherry red, cool, replace.)
If you use a sand-blaster to clean the electrodes (only!), a few seconds will do the trick. Longer is likely to lower their lifetime.
I used to give the neighbor boys old plugs. They pretended they were space ships and rockets.