Well, there you have it. You basically need a new truck! (OH! ... just kidding!)
Really, you have a working list. Now go talk to your GM mechanic. See what they recommend. If you go prepared to do any and all of these things, and they say it's not necessary yet, then I'd wait.
You're prepared to pay, no see how much you really don't need to pay (yet), that can wait for another day. If they say do it all, then ... there ya go. You have the final word on what you can afford and what is most important and what could wait till the next oil change or even the one after that.
Your call, but after all the advise here, I'd now ask my GM repair shop.