Blowing up
FD, you may be further ahead to sell your propane BBQ and buy a brand new Natural Gas one. By the time you find the components to change the propane one to NG and buy the disconnect for the gas line, it may be about the same costs.
Also, alot of propane BBQ's are not certified to be converted (Fiesta is one ). If you do and there was ever a problem (fire, explosion) you would have some big problems with your house insurance.
You will love the convenience of the gas BBQ, nothing worse than running out of propane when the steak is half cooked.