For a weekend toy you won't notice any difference from valve weights. If you're running 10 grand then the added weight affects inertia and then you've got to adjust the springs & they're out of balance etc. etc. The seat overlap is no big deal as long as the actual contact areas don't touch.
I fit the valves, turn the head on its side and fill the ports 1/2 way with alcohol then blow around the valve with an air gun. Sometimes all they need is a quick lap to bring them in. Sometimes it's a crappy job. Hopefully your retired machinist has had enough experience to do the job right.