Towing with a lifted truck as long as its a bumper pull is no worries. You will need bags in the back and a mega dropped hitch.... But that duramax will haul the mail with a trailer behind it. I put stupid miles on Miles truck when it was mine with my bumperpull and buggy all over the country.
What you need to look for or worry about.
Pump Rub- transfer case. the pump vibrates, and the steel clip holding it breaks and rubs a hole in the magnesium case, you loose your fluid and it burns up
$175 fix from Merchant Auto
http://www.merchant-automotive.com/transfer-case-pump-upgrade-kit.aspx
Front Wheel Bearings- with anything bigger than stock the GM Unit bearings self destruct. Jack the front up and grab the tire at 12 and yank it forward and back. if its got play you need bearings.
All things steering- Tierods, Pitman, Idler, Steering box. While the front is jacked up grab tire at 3&9 and jack back and forth much movement? then its got problems. Cognito is what you need. HD Tierods, and the Pitman Idler support kits. Lifted without the Cognito support you'll get 5-7k out of pitman and idler, with support kit 15-20k out of them.
If it doesnt have all the Cognito **** plan on a grand for all of it and do the Upper Control Arms while you're at it to get it back to Cadillac Smooth.
Rear Axle outer seals.
Fuel Filter housing cracks
And you have to stay ontop of the tire rotates and getting the ****er aligned. IFS will eat tires like no other. I know y'all dont have a Firestone in Paola, but $99 lifetime align and I align mine every oil change 5k.
I've owned an '02, '07, and '06 Chevy HD Duramax's
'02 was lifted 6"
'07 was turned up for 19.5"s
'06 is Cognito'd the **** out on the front for everything I learned on the others.