4.2L V6 - 2003 - 135,000 miles

It looks like I have the famous isolator bolt issue, my mechanic also thinks I need a new valve cover gasket due to oil stains around the engine below the valve cover.

I'm aware of a gasket issue where coolant leaks into the cylinders (head gasket I assume?). Is that worth tackling while I do these others?

Is there anything else I should tend to while I have things opened up?

 

Might as well do the intake gaskets while you are in there. It isn't much more work while it is down that far and the V6 is prone to intake gasket failure that will leak coolant into a cylinder and make you think it is a head gasket failure.
If you're feeling froggy you could go ahead and do the head gaskets too, but if it needed them you would already know it for sure.
Other than that get everything squeaky clean, put it back together and drive it.