90 - Engine cuts out, doesnt charge/bad injectors

1990 Pontiac Grand Prix STE
3.1L V6 Automatic
~215K mi

New battery, alternator, year old wires+ plugs

Here's the deal - car refused to hold a charge, so I put in new batt and alt. Same deal. Living in Chicago, I haven't driven it for 2 months. But now it's doing the same thing.

Once I finally got the car started (Midas got it going and reported the alternator as 39A under spec) it continues to do the same thing. You put it in gear, the engine cuts out. Come to a stop, it cuts out. Have to shift to neutral to keep it going. Cuts out while driving. Restarts fine if I put it in neutral, and it still takes off like a beast.

I took it to a recommended mechanic and he said the alternator is fine - it's my injectors. And I leak oil, apparently from everything. I can deal with leaking oil, for now, but I want my frikkin car back cause CTAing to the south side sucks (I live in far north).

He told me to do the injectors (which are about 80 each) and give it a tune up (I'd need new plugs too I guess) I'm looking at around $600 or more. While I can afford this, it's a huge chunk of change I'd rather not pay.

You guys are smart. Any ideas? Could it be something else? I think it's the injectors too. How hard is this to replace myself? Any ideas would be appreciated here.

Looks like I'm not driving my ride to detroit this weekend...

hello i have a 91 grandprix with a 3.1 and it died on me while driving a couple of weeks ago and kept dying on me every few hundred feet till i got it home ,yea it started just fine but it kept dying none the less,it turned out it was a bad fuel injector that was screwing up the others,the fuel injector i got was used it was 42$ the mechanic charged me 284$ part and labor good luck