I'm loosing coolant somewhere, and I can see some pooling just below the plastic upper intake manifold in a couple of little valleys. Could it just be the gasket or is it most likely the manifold? ALso, I called the dealer to price it, and they said I should replace the lower intake manifold because it'* been redesigned... the 2 together would be over $500!!!.
What have others done??

Here'* your answer as to why GM wants to replace your Lower Intake:
Engine Coolant Consumption or Coolant Leak
(Inspect for Material Degradation/Replace Intake Manifolds) #01-06-01-007A

Models:
1995-1997 Buick Rivera
1995-1998 Buick LeSabre, Park avenue
1996-1998 Buick Regal
1998 Chevrolet Lumina, Monte Carlo
1995-1996 Oldsmobile Ninety-Eight
1995-1998 Oldsmobile Eighty-Eight
1998 Oldsmobile Intrigue
1995-1998 Pontiac Bonneville
1997-1998 Pontiac Grand Prix
All With 3.8L Engine (VIN “K” – RPO L36)

Comment:
Some owners may comment on excessive engine coolant consumption, or an engine coolant leak near or under the throttle body area of the upper intake manifold.

Cause:
Upper intake manifold composite material may degrade around the EGR stove pipe and could result in an internal or external coolant leak.

Correction:
1. Follow the upper intake removal instructions found in the Engine Unit Repair Section of the Service Information Manual.
2. Inspect the inner diameter of the EGR passage for signs of material degradation. Degradation will appear as “pitting” of the composite material in the EGR port passage.
3. If degradation of the upper intake manifold composite material is found, replace the lower and upper intake manifolds with the following part numbers:
> Lower Intake – 24508923
> Upper Intake – 17113136 (includes necessary upper intake plenum gaskets)
> Lower Intake Gasket – 12537197
4. Follow the lower and upper intake manifold installation instructions found in the Engine Unit Repair Section of the appropriate Service Manual.
5. If degradation is not apparent, skip to Step 7.
6. Verify the repair.
7. If no degradation is found, evaluate the vehicle for other causes of excessive coolant consumption as noted in the Engine Diagnosis Section of the appropriate Service Manual.

So they've revised the lower intake, but have they made any changes at all to the upper intake in the 7 years they've been using it?

Because the lower intake has been revised, that problem developing again is miminal. I, personally wish they (GM) would just replace the "Plastic" upper intake with a metal alloy one instead. That way, the tendency to warp would not happen, hence no leaks. I've got an old Series II lower & upper intake here that I'm planning to do some work on & see if i can arrange a better setup than the plastic upper.

I've receently [Two weeks ago] replaced both of my gaskets I ordered my gaskets thru GM direct. The cost on labor will vary but $500 is way high. I had the stage one kit from ZZP, a new water pump and the new gaskets and the labor bill was under $350.

I'm not talking about the gaskets costing $500, I'm talking about the upper and lower intake manifolds costing over $500.

So do both the upper and lower have to be replaced? Or just the upper?

This interests me as well, cause my bonnie my have such leaks as well. However, I'm dealing with a pissed off tranny as well. (Beginning to see why this car got traded in...) Anyway, does it need to be addressed quickly? Like, is that coolant leaking into the engine critically bad or can it wait till after I get the tranny fixed (or give up)?

Darn freaking plastic

I thought just the upper, but when I called the dealer to get a quote, the guy said that the lower manifold should be replace at the same time, because it'* been updated so that it lessens the chance of the upper plastic manifold from warping/melting again.
I asked him if there were any recalls or secret warranties or goodwill warranties, and he said no, I said it was a ripoff, and he agreed. He said they see lots of them, change about 2 or 3 a month.

I think some guy from Iowa designed it. (snicker)

Mine seems to be leaking in front of the manifold between it and the valve cover, just to the left of the Tstat housing, in a couple of little valleys there.
I don't see any symptoms of it leaking into the engine, but it seems I read a post here about a guy who had coolant leaking into the valley and getting into the oil... that would be a bummer.