1996 Grand Prix SE. its a good car......kinda.

I need help with weaning out the possibly large and expensive costs of polishing this turd. anywho. let me set the scene for ya. last Monday morning, -4 degrees. snowing, wind blowing and colder than a witches tit. the car start right up, no problem. heated up enough for me to bare the 30 minute drive to work. on my way to work,as I approach the first stop coming off a 65mph highway. the car starts to lose power (low RPM, lights start to go dim,and just sounds like the car is about to just shut off) luckly, it didn't die....at that light anyway.
one mile down the road I approach the next light. as I get to the light i start to brake, RPMs start to drop, lights stat to go dim again. as I come to a complete stop, the car loads up, RPMs spike to about 2,000  and the car just shuts off. in a panic I try to start it again and the car barely, and I mean barely tries to turn over. with each crank I think the motor only turned about half of half of a turn. absolutely dead in the water I push the car to the side and wait for a coworker for a pickup.
15 minutes go by as he pulls up, I try to start the car one more time. it fires but wouldn't stay running. late for work already I leave the car there.
after work we go to try it again and lo an behold the car starts an I make it back home no problem.
now for one whole week this happens, just in different spots around town even in the parking lot of my jobsite. car would start, get so far and then eventually load up and die. most time it happens is wen I put the car in park. but also does it in any gear. reverse to drive, park to drive, etc etc.
any advice will help. ive been told bad alternator and bad battery, intake valves gummed up and bad gas lines/intake.
please, any help is appreciated!