Welcome from NJ. I owned an 08 Avalanche for 10 years so pretty much the same truck you have, The GMT900 platform was excellent although not without its quirks.
I agree with
@swathdiver on the OE parts and severe maintenance. A lot of the general public/owners have issues with AFM/DOD lifters etc, but if you change the oil regularly between 3k & 4k you shouldn't run into any issues, Had 160k on my Avy and never had an engine tick.
Change the trans fluid every 25k or less and add a trucool 40k after the radiator plate to keep the trans temps low and that should extend the life of that 4L80 trans.
If you are looking for a little more power, before you dive into adding parts....get yourself a tune either from a local shop or reach out to @bentuneperformance on Instagram.
