I replaced the 3.1 intake gasket on our 99 Cutlass (Malibu clone) some time ago and no problems so far. Other than that the car has been reasonably dependable as a daily driver for my wife.
If you are reasonably handy as a mechanic and have a full day to kill, you can do this yourself and save a ton of labor $$. I used the updated Fel-Pro gasket and also replaced the injector o-rings when I re-installed them back into the intake. Also, in my case, the fuel line attachment to the fuel rail was the original factory attachment that took some muscle to break loose after loosening the attachment note. You MUST use an o-ring to re-connect this or you'll get fuel all over the place. New valve cover and upper plenum gaskets were also installed.
Keep in mind that the pushrods go through the gasket and that you will need to unbolt the rocker assemblies to install the new gasket. These are not hot-lash adjusted so you just have to keep everything in order and then re-install the rockers and torque to specs. Speaking of that, I used some lock-tite on the intake bolts and torqued them to spec - they are kind of puny and I can see why they tend to loosen.
Cost me some time and about $50. I also added some 3M rtv to the corners of the intake and then let the whole thing sit overnight to ensure that everything had cured properly. I refilled with DexCool as well, later will do the G-05, but there were no sludge issues at all with our car, so I just replaced the coolant.
I used the Haynes manual that seemed to cover this repair fairly well. It's silly that this is a known defect on these engines though and that GM turns away if you are out of warranty. For me, the car is generally OK, but the customer support is non-existent, especially for the now-defunct Olds division - that is the reason I will never buy GM again.
