Welcome!

Sounds like you're starting out with reasonable expectations which helps! You're not too old to learn. I'd spent years as a tech moving from independent shops to GM dealerships when I found my way into tuning. Back then you had to work much harder to find the answers since the GM chips were still a mystery to most people. But I've learned enough to be dangerous and I have no doubt you could do the same. BTW, you'd be surprised just how much information is buried in the old GM manuals. The GM engineers did a great job laying out basics using the actual GM programs to draw from. If you have a manual for a 7747 equipped truck it might be helpful to have it available while you learn.