Many times when a crank position sensor starts going bad it will make your rig crank, and crank, and crank but no start. Crwal under there and see if the two bolts have loosened up. If those are tight, you can loosen them and re-seat your cps and see if that helps, they tend to wear slightly and at times it can be enough where you have to "adjust" them.
You can perform a conntinuity (I know, very bad spelling) test with a meter. It should show an open circuit. If its closed then its bad.
With stalling issues check out you IAC (idle air control) they can go bad and cause stalling issues, also they get very dirty after awhile (carbon and gunk). Take it out and clean it and place it back in, reset the comp and see if that helps. I forget right now (im at work and away from my FSM) what meter test you do on it, but try cleaning the IAC.