I was told that sometimes GM have computer updates for your truck. How can i know if there are any updates available for your truck before you take it to a dealership for a charge. Any ideals?

Yes, you are correct. Sometimes GM puts out updates just like Microsoft would with there software. If you can read the sticker on your PCM, you will see a long bold #. Now, goto this website, and type in your VIN # and it should tell you if there is an update for your PCM.
TIS

Last time I knew, CAL ID #'* are sequential. If you see a number listed that is higher than yours, than you know there is an update. But this doesn't mean that it is a crucial update that needs to be done.

GM Vehicle Calibration Information



VIN: 1GNDS13S742385394
Controller: PCM/VCM Powertrain/Vehicle Control Module



Calibration History for: Operating system
Part Number CVN Bulletin # Description
12597031 N/A - New software to reduce the potential for setting P0335, P0606, and P0741.
12590965 0000EBB6 - New software to address P1680.
12589825 N/A - New software to enable P2771 diagnostic.
12587608 N/A - Software change to improve performance
12584594 N/A - Operating system

Calibration History for: Engine
Part Number CVN Bulletin # Description
12600286 00009584 - Calibration to address coast down idle roughness and revise cruise control operation with less vehicle speed deviation. Also contains diagnostic enhancements for DTC P0171.
12597034 000055D9 - New calibration to reduce the potential for setting P0335 and P0606.
12596378 00003A2F - New calibration to reduce the potential for setting DTC P0606.
12590969 00001D8E - New calibration contains diagnostic enhancements and improves idle stability.
12589854 00001934 - New calibration to enable P2771 diagnostic.
12588421 00006391 - New calibration to address DTC P0172
12587518 0000D44A - New calibration for start of production
12587105 00002F48 - Engine calibration

Calibration History for: Transmission
Part Number CVN Bulletin # Description
12597046 000081A1 - New calibration to reduce the potential for setting P0335 and P0606.
12593020 0000CBD7 - Improves transmission performance in cold garage shifts and addresses rough 1-2 shift.
12588434 00001F0D - New calibration for transmission shift improvements
12587118 00006146 - New calibration for start of production
12577612 0000D8BA - Transmission calibration

Calibration History for: Speedometer
Part Number CVN Bulletin # Description
12577630 0000CCF9 - Speedometer calibration

Calibration History for: System
Part Number CVN Bulletin # Description
12596423 000052C6 - New calibration to address customer complaint of overheat condition.
12588441 000075E6 - New calibration to correct problem occuring at the assembly plant. Does not address any service issues.
12587260 0000C710 - New calibration for start of production
12587125 0000F060 - System calibration

Calibration History for: Electronic Throttle Control
Part Number CVN Bulletin # Description
12577594 N/A - Electronic Throttle Contro

Uh yea...with those many updates, yea, I'd get it updated myself. Print that page out before you goto the dealer to have it done. Just incase they think your a looney.

tis will not let me check my vin #

What won't let you check your vin #?

TIS, the website posted above. I just tried the VIN that was posted already, and was denied. Looks like they may have pulled the plug on this...

you should be able to call the dealer with your vin, because if the update was done on your car it would be logged against it in their database