1996 Chevy Tahoe MY 1996 THAOE WONT START

WHEN I TURN THE KEY ALL THE DUMMY LIGHTS COME ON AS USUAL BUT THE ENGINE MAKES NO NOISE. I IMMEDIATELY THOUGHT IT WAS THE BATTERY SO I TOOK IT OUT AND HAD IT TESTED AND IT WAS FINE SO I THEN PROCEEDED TO THE STARTER AND DID THE SAME TO FIND OUT ITS NOT THAT EITHER. SO I PUT EVERYTHING BACK IN AND CHECKED ALL THE FUSES AND RELAYS BUT THEY ARE ALL GOOD AS WELL. SOMEWHERE ALONG THE WAY I AM LOSING VOLTS. I CALLED AND SPOKE TO A MECHANIC AND HE SAID THAT IT COULD EITHER BE THE IGNITION SWITCH OR POSSIBLY THE NEUTRAL SAFETY SWITCH, IS HE CORRECT OR DO I HAVE BIGGER ISSUE ON MY HANDS? I AM COMPLETELY STUMPED AT THIS POINT AND EXTREMLY PISSED OFF CAUSE THIS IS MY ONLY VEHICLE. ANY INFORMATION YOU COULD GIVE ME WOULD BE MUCH APPRECIATED.