I am with Mike on replacing the whole upper intake, the redesigned ones have strengthened baffles so you supposedly don't risk having the upper intake explode if the fuel pressure regulator diaphragm ever fails.
I don't think any changes were made with it in regards to coolant leakage though, well other than the reduced diameter EGR Stovepipe, that helps keep the EGR Coolant Ports cooler, that way they do not warp around the coolant ports that go into the upper intake manifold/throttle body.
One thing that can happen with the upper intake manifolds is the plastic channel that holds the throttle body gasket in place can warp, but usually that only makes it leak externally.
I cannot think of what would cause the coolant to get into that part of the throttle body though, it would have to be a lot of coolant leaked inside the upper/lower intake manifold for that to happen.
Let me get you some part numbers, if you still need info on the installation I can provide it, I have pics of the bolt tightening sequence posted already somewhere on here, as well as videos from the job being on on a supercharged 3800 II, which the gist of that process is the same as on the naturally aspirated motor.
DORMAN Part # 615180 - Upper Intake Manifold with new gaskets and reduced diameter EGR Stovepipe.
The link above is for one of the cheapest places I have seen the manifold sold at, if you want to be sure you have a more reliable warranty on the part, then get it from RockAuto, you will pay a few bucks more, but they have better warranty policies than Amazon.
FEL-PRO Part # MS98014T - Lower Intake Gasket - Cheapest place for this that I have seen is RockAuto, so you may want to order them both from RockAuto.
DORMAN Part # 47065HP - The Aluminum Cast Coolant Elbows, RockAuto carries them as well, but they are not always in stock, if they are not check a local auto parts store, just be sure they are aluminum.
A tip for the EGR Stovepipe that is on the Lower Intake Manifold, use some channel lock pliers on it for removing it, you may have to tap on them with a hammer a few times, but it should come out, when it does use the old one to tap the new reduced diameter one into place, it will fit over top of it well, and make installing it just right easier.