I just did all this on my 1998 Firebird with the 3800; someone put a reman engine in it at some point (going to suspect intake gasket failure as well, as that's about the only way you can kill one) and whoever installed it used only RTV and no o-rings between the upper and lower intakes where coolant flows up into the throttle body which was, of course, leaking.
Went ahead and replaced upper and lower intake gaskets (lowers were practically brand new upon inspection but the same person who used RTV instead of an o-ring also cheaped out and put plastic lower intake gaskets in, so I replaced with metal while I had most of the work already done) along with valve cover gaskets, both radiator hoses and the heater hoses because they were so soft it felt like I was going to rip them pulling them off. I've almost got everything buttoned back up after working on it for an hour or two here and there over a couple weeks.
Its not the most fun in the world to have half your engine literally under the dash. I'm sure that made it take far longer than it should have!