Engine won't start

Transmission problem V8 Four Wheel Drive Automatic 150000 miles

Installed a rebuilt torque converter, rear main seal, also had the forward clutches in my transmission replaced by a good trans shop.

Everything went back together smooth. Now truck doesn't start. Turns over fine, but will not start. Never had problems with starting before. Check engine light also on, was not on prior to removal of trans. Do not own tester, unsure of what codes being thrown.

Any help appreciated. Is it possible that a wire got nicked, not allowing the engine to start?

Update, found an individual with similar problem. Answer there was to replace the park/neutral safety switch. I could not get the two connectors on this switch to fully "click" into place. Is this a problem?