Replacement of Crankshaft position sensor on 1999 Chevrolet Silverado 1500

Changed the Crankshaft position sensor and now my truck will not start. Before changing the crankshaft, my truck would stall until it got hot and then it would work fine. What do I need to do? Thanks!!

Verify the sensor is the proper application - a diagnostic tool should be hooked up to monitor crankshaft signal when cranking the engine to verify it is functioning.
OK. But what has me concerned before changing the crankshaft sensor it did start and would misfire at a high RPM and it will not even start.
This is why I suggested checking to make sure you have 1) a genuine Chevrolet part that is correct for the vehicle and 2) then check for crankshaft signal with a diagnostic tool.

Sorry to say that everything else is totally guess work. Technicians try to approach issues scientifically, by eliminating variables first (in this case - a sensor of unknown quality was installed, now it's a no start), and then doing proper testing next (monitoring and checking for a signal from that changed sensor).