I'll def. do the exhaust valve ....I've been reading that you may not need hardened seats with a SS valve too ...... is there a large diff in cost if you just enlarge the valve without hardened seats ?
The cost is going to depend on the machine shop, and I would likely do it anyway for peace of mind, I don't remember the cost breakdown on everything I had done, but I am one of the lucky few that can get a family discount at a local shop. I don't remember the hardened seats being a huge chunk of the cost though.
It's only a matter of time before the cost of adding lead substitute to your fuel equals the cost of having hardened seats installed.
One thing I can say for sure, if you don't get the hardened seats and end up down the road with compression loss from a cracked head you will be kicking yourself in the *** for not having done it.