You frustration is understood, these cars have a long list of little issues that develop over time that can really degrade their performance, reliability and fun factor. It's cool that your the original owner of this car.
Maybe start by letting us know where your located, there may be someone near you that is experienced with these cars that can help you out.
If your car has 100k on the clock there is a long list of items that can be addressed that will get you back to "as new as possible" condition. This is assuming the engine itself is healthy with good compression and leak down numbers, not to mention the transmission.
The link in the previous post to Vortex Buicks is full of excellent info, but can be overwhelming.
Here is where I would start:
-Go through the fuel system (pump, filter, check line condition, hotwire kit, new injectors)
-New ECU Chip from Turbo Tweak to match these injectors (much better for the modern fuels and performance)
-Re-gasket the top end of the engine (minus cylinder heads) to address any vacuum and oil leaks and gives a chance to clean things up.
-MAF Translator with new MAF
-Replace the stock timing set
-Replace the stock valve springs
-New spark plugs, plug wires, O2 sensor and check the condition of all other sensors.
-Ensure there are no exhaust leaks (cracks in the stock headers cause this and bad seal at the cylinder head)
-Remove the CAT from the exhaust.
-Consider adding a scan tool like a SCANMASTER
I'm sure I'm forgetting some items, but as you can see the list is long. At 100k on the engine I would imagine most of these items have not been addressed, each will cause little issues and all together can add up to a car that's not the same as it once was.