Nice review. I'm 22 and own a 95 Buick Park Avenue, so same era and platform as your car. Wouldn't trade it for anything else.. well maybe the last generation of Acura TLs before the current ones if I could afford it.
Back on topic. Good to know that you are aware of the intake manifold issue. I just replaced my UIM and lower manifold gaskets last week. I assume they had around 80k on them. 55k that I drove myself. Both were shot. Replaced it with a Dorman UIM, which is better than the GM UIM and cheaper. I also replace the lower gaskets with GM's aluminum gaskets.
At 80,000 miles, if your car has the original manifold, you are waiting for a disaster to happen. I can guarantee that the LIM gaskets are shot, and the UIM is a ticking time bomb. You should just consider it preventive and normal maintenance. The manufacturing date is imprinted on the manifold. Can be done for around $200 DIY, and is pretty straight forward.
Just to clarify. UIM failure does not cause leakage into the oil. It hydrolocks the engine if not caught in time, which can be very bad. But it shouldn't cause any damage if caught in time. The LIM gasket failure will cause oil and coolant to mix, and this is bad for the bottom end of the engine as stated. If you do this repair, you cannot do one without the other; they go hand and hand.
Also of note. UIM and LIM gasket failure can be very slow. My car has been consuming a small amount of coolant for probably more than a year, but got worse recently. I was consuming 8oz of coolant per 500 miles. Which isn't that noticeable of a drop in the coolant reservoir. Just some info for anyone that may run into this.
I hope you get to enjoy your car for many years to come. The 90's GM full size cars with the 3800 are some truly undervalued cars, and are a steal for the money.
Thanks for the great comments. Also, thanks for correcting my errors.
Now some C-Body talk. My grandfather's current Cadillac, a 1993 Sedan DeVille just went into the shop for a new power steering pump. After changing the pump, the mechanic noticed that the mounting points for the engine cradle, which supports the engine, transmission, suspension, and steering rack, on the undercarriage of the car actually rusted off. Typically, on these GM H- and C-Body cars, the washers used on the engine cradle bolts will rust off one by one. (I believe there are six, total) In the case of my grandfather's car, it wasn't the bolt, the washer or the actual cradle itself, but it looks as if someone used an acetylene torch and cut a circle in the floor of the car where the engine cradle bolts to the undercarriage.
The owner of the shop recommends not driving the car. He claims that the next bump could send the entire cradle to the ground. With no other solution in sight (no one thinks that welding would be a solution in this case), we might have to salvage this poor DeVille with its absolutely mint paint, interior and engine/tranny.
If anyone else has a C-Body or H-Body GM car, and you live in the snow-belt, I would definitely consider checking the integrity of the engine cradle, its bolts, washers, and bushings, and the mounting points, too.
I agree with the critique of the UIM. I have a 3800 out of one of these very cars that has spun the number 1 rod bearing due to that very failure. The good news is the engine is very rebuild-able if you want to take the time.
I happen to love this car, and it's been in the family since it was purchased new.
Interesting fact: The 1998 Regency was the last car to carry the old 'rocket' emblem; all of the other 1998 models carry the new stylized version.