Software updates must be done at a dealer, or at the very least, at a well-equipped independent shop. (Requires a Tech 2 or a programming interface module, plus a subscription to GM TIS for the software itself).

To my knowledge, GM does not print paper manuals anymore. Helm is the name of the company that used to do so, and they might make one for consumer use, but dealerships don't use paper copies at all, it's all electronic.

Aftermarket manuals vary in quality, but I've never seen any of them that even come close to the information in the factory service manual. Also, a code reader will not give you the trouble codes you need. It requires a scan tool that has the ability to communicate with the ATC system, so this typically means investing in a professional quality scan tool, just to get the trouble codes.

The Tech 2 will tell you what the current software level is, but you'll still need to subscribe to GM's TIS website in order to see what the latest release is, and what it addresses.

The short answer to all of the above: it's pretty tough to do this on your own, unless you're really equipped.

Now....

If this truck rolls into my shop, the first thing I'm doing is seeing what the trouble codes are, followed by looking at applicable TSB's, and following that with researching software updates to see if any of them address the problem at hand. At that point, I would probably just update the software out of convenience since I'm already there with a scan tool hooked up. You could probably expect to pay me for an hour of shop time to do all of that. Some techs will charge you more to update the software..... I see it as part of the diagnostic process, it needs to be the latest software before I invest any parts into it, so that is a variable you might come across.

You plan on $100 to diagnose it, and if it needs an encoder, you can plan on spending about $400 on that, plus another $80-100 to install it. You're a DIY type, though: you can replace an encoder motor pretty easily, and you'll find that they cost less out in the aftermarket, too. It might need a switch, we had a lot of trouble with switches, and those cost about $80 or so.

If you want to take it in, ask them to update your software, tell you what codes are in it, and give you a diagnosis, I think you'd reasonably expect to pay $100-150 for that information. I know that's a lot of money, but this equipment is expensive and any shop needs to get a return on that investment.