they should NOT have done anything to the jug until they had the new piston. you have to have the piston to get the correct tollerances. since they touched it, I recommend a minium of .040 over stock sized piston to be certain they can get it to fit the specs. if your redoing it, may as well repalce it with a weisco performacne type piston. it increases compresion from 9:1 to 10.25-10.5:1 compression. even though they said the valves were ok, I would still take them out of the head and check the srufaces. if you have a lip on either valve then you ned to repalce them both due to wear. ($30 shipped it's a cheap fix) also you can then replace the valveguide seals while your in there. you can do a basic valve lapping to get the new valves to seat since it's just a basic fix.
but me, I'd for sure do the piston.