I've been getting by on a second set of heads but will be right behind you in the cylinder head refurbishing pretty soon. So I'm not an expert.
I believe the exhaust seats are the ones that get replaced. Intakes run cooler and don't have a problem.
I think the rest of the work has to be checked before knowing if it all gets done or just some of it. Has your brother done Airhead valve work before? You seem to trust him. The heads are heated up, very hot, and the old guides driven out and new guides driven in. Then the guides are reamed. Sometimes the intake valves might be reused. But having 4 new valves also sounds nice.
If you are really looking to make some improvements consider adding dual plugging while the heads are being tended to.