Car won't start..told it might be Timing chain

i have a 1991 g20 and one day it just didn't start. i had a mech. check it out and he said it was the timing chain . he said it jump a couple of teeth on the sprockets. what can i check first so i dont have to asume its the timing chain..oh and it cranks really slow/hard when i crank it like its being slowed down. and the spark coming from the distributor is red not white. so im asuming its low on voltage too.. please help