98 Silverado starts then immediately stalls
Hi guys, new to posting in the forums but I've been reading them for a long time. I work at a landscape shop and we're having a problem with our 98 silverado 2500 5.7L. We've been using it to plow snow and it worked just fine the other day. We parked it overnight as usual and when we tried to move it in the morning, it wouldn't shift from park. Left it running for a 1/2 hour or so and tried it again and it worked, and I pulled it into the shop to check fluids, powerwash, etc. Went to move it again and it wouldn't shift from park. Took the column apart and got the shift interlock lubed (it was sticking) and put it back together. Now the truck will shift from park with the key and brake on, but when I try to start it, it will start but immediately stall out. I've checked fuel pump voltage, relay, fuse, and pressure at the rail, I've also checked the oil pressure switch, all the necessary fuses, and replaced all spark plugs and wires. I'm at a loss. The truck has taken more cranks to get to start for about six months, but it always started and ran fine until now. I'm thinking it's the ignition coil or ign control module but I don't know for sure, and I don't have anything to pull codes from the diagnostic connector. Any ideas on where to go from here or should I just have it towed to a mechanic?