2003 P.T. Cruiser shuts off.

my 2003 p.t. cruiser has been shutting-off on me and showing an error code P0016. My mechanic took out the crankshaft sensor to the auto parts store and replaced it with a matching one. The car still stalled a few days later. This time the auto-parts store asked for the car VIN# and gave my mechanic another crankshaft sensor based on the number. Well, the new sensor didn't fit! My mechanic asked me if the engine in my car was the original one. I said I don't know because I bought the car used in 2006.
He thinks the best thing to do at this point is to replace both crankshaft and camshaft units so they match and the computer then will recognize the communication between both. What do you think?