Suspension upgrade for towing

I purchased a previously used 2016 limited; double cab; under the impression it was all stock parts. I spent last summer towing a 32ft trailer for long distances (2-5hr each trip) using a WDH, under the set-up instructions of the sales dude. IMO the rear end always had major squat when attached; and now I am getting squeaking noises when I drive over roadbumps, potholes, etc. Apparently, I have been driving and towing (6000lbs!) with deflated firestone airbags and what I would presume is shi*** attachment of the WDH.
I can't imagine another painful conversation with the Toyota service dept here; but I wondering what my potential damage might look like at this time...
As a newbie, wanting to learn and upgrade my trucks performance and esthetics, I was leaning towards a 2" lift to allow for 33" inch tires and better towing capacity by upgrading my suspension. (Of note, as I just removed my front grill and bumpers for a chrome delete), it looks like the previous owner did a CMC on the passenger side, but I have stock tires and wheels).
What is the best route now...? I apparently have the bilstein 5100s in the front, but unsure of the settings; it was suggested I had room to raise them a bit. (Also some confusion here as the truck was sold as "stock") ...
From what I read, I should ditch the airbags completely (not replacement them); get bumpstops and rear sway bar and properly adjust the WDH. Haven't looked too much into anything else at this time....
Should I consider replacing most of the suspension components given the potential damage? What is the preferred upgrade options? Also...can I do it myself Thanks!!