Engine cranks and dies immediately?????

I have read a few posts that talk about a 1999 GMC Suburban that starts and dies immediately. This problem is come and go. It seems to be worse if it sits for a while. After trying to start sometimes it dies a few times and starts and runs fine and sometimes you have to come back in a few hours and it starts right up. Most times it starts with no problems. A mechanic shop told me today it is the passlock sensor and wants over $800 to fix. I have never heard of this problem before now. Any ideas or fixes that some of the others on here have had?

If it is the passlock how do you reprogram after installing a new one or what should a reasonable price be for having a new one installed

I would replace lock cyl to start with

Does the new lock cylinder require reprograming of the passlock? How would I find the process of reprograming. The manual I have does not even mention passlock and information has been hard to come by.

does not nead programing