My wife's car is a 1989 Bonneville LE. Recently, she complained that it wasn't running right. I drove the car for a couple days and picked up on the symptoms pretty quickly - hesitation, bucking, extremely difficult to start if it was at operating temp.
We have had the car for maybe 6 months and haven't had any engine trouble with it, though occassionally it will slip under heavy acceleration when cold. Knowing that it hadn't been used much in the last couple years by the previous owner, I decided to try some stuff, but firstly I would check the codes.
Car has had a code 41 (cam sensor) since I bought it, so I decided maybe the cam interrupter magnet was gone. Replaced it and the cam sensor, no change. Also got a code 44 (fuel trim) so I took a wild stab at an oxygen sensor. No change. Bad ICM, since it only happens when warm? Replaced that and the ignition coil, no change.
So after hitting many dead ends and doing a complete tune-up (fuel filter, air filter checked, new wires, new coil pack - plugs are next week) nothing changed.
So I turn to the internet and do hours and hours of research, and many people have had these same symptoms with a bad fuel pump. So I had it changed by a shop because I was working, and it fixed my problem. Car runs great again!
Somwhat did I learn? Well, it's a mixed bag. I work for a parts store, so even after buying parts I didn't really need and installing them, plus paying $100 to have the fuel pump installed, I am still out less money than most people would be just to have it taken to a shop, diagnosed (and possibly misdiagnosed several times) and fixed. In the effort, I have a bunch of new stuff that was never replaced by the previous owner (I have their records.)
All I would pass on is, PLEASE, check your fuel pressure if you have similar symptoms with any car, but especially a 3800. Might save you some money in the end! Or do it my way, and have a lot of new stuff under your hood. Both methods work, technically.

I always run mystery oil in my tank ever 6 mo. and never had a fuel pump fail.
Dissolves all the crap on the pickup screen.

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90 SSE Bonneville Sold but not forgotten.

Well, at least you got it fixed.
$100 for the fuel pump installation sounds like a bargain.

It's best to always start with the basics.
Testing, though inconvenient, does save you money.
This site has some good step by step instructions on how to troubleshoot a number of issues, including testing the fuel pump
http://troubleshootmyvehicle.com/gm/3.8L/index-of-articles-1