I don't see any mention of a water pump--you should absolutely replace that. You probably won't need any sort of sealants. I didn't use any when I did mine (aside from a dab where the valve cover gasket needs to bend).

You mentioned hushers. Have you checked your valve clearances? I know you get the hushers and fuel injector seals with the head gasket kit, but it's not strictly necessary to replace them at this time... and if you're doing the hushers, you're taking the cam off and may need to buy valve shim disks because those new hushers will change the clearance a little.

When I got to this point on my second Volvo, I decided to go for it and replace the valve stem seals, order some shims, and lap all of the valves. I think it's worth the time invested in labor, but you'd have to order some tools and parts.

Other stuff you might consider doing when the head is off are cam, crank, and intermediate shaft seals. While you're working on the intake, take the opportunity to clean the throttle body and make sure it's adjusted correctly.