Does attempting to jump the car make any difference? Have you checked to see what kind of power the charging system is putting out with a multimeter?
I'd first try to rule out any electrical problems. Make sure that you have good connection on all your grounds, and that the battery terminal posts are not corroded and are capable of tightening down firmly. I'd also make sure that you're getting power to the starter. If that checks out, I'd suspect the starter as well. Sometimes, tapping on the starter with a hammer can get it to work (did that with my 3.1 turbo GP for a long while before it finally completely gave out on me). At the very least, if it makes any difference while tapping it, you'll know it's the starter.
If the starter needs to be replaced, I'd replace it with a newer style high torque starter off a 3100 or 3400 (hint; look for a '00 & up Impala). Because those motors were produced until around '05ish, you can find a lower mileage used one at a junkyard fairly cheap, where as you do NOT want to buy a 20+ year old used OEM one off a 2.8/3.1/3.4DOHC for a replacement, especially given how much of a pain in the ass replacing them is. The newer ones are an upgrade, as they are much smaller, much lighter, high torque/faster starting and bolt right up to the old 2.8/3.1/3.4DOHC motors since the 31/400 are essentially the same block. And due to the much smaller size, they are MUCH, much easier to get back on to the motor vs. the original/OEM replacement. Trust me, you'll thank me later when you see how much of a pain removing the old one is.