Why won't my truck start after replacing the crankshaft position sensor?

I took my 2001 Chevrolet Silverado
2500HD, long bed, single cab, base model,
6.0L, gasoline, down to get the check
engine light diagnosed when it came on
and started running like Crap (mainly in
lower rpm's, most of the time better in
higher rpm's. They said it was a misfire of
spark plug 8 and crankshaft position
sensor. Well at that moment, I only had
enough for spark plugs (come to find out
way later on, I had some already).......
Yep!....... Well I installed those, then two
weeks later, replaced all the wires as well.
And now 3 weeks later, I got the "CPS". I
installed it today, and now my truck won't
start. It sounds like it wants to, but just
won't get over the hump to start. Any help
would be GREATLY appreciated!!! Thank
you!