How many miles? First thing to do is make sure it is fully serviced - change fluids as needed based on miles, check the air filter, cabin air filter, and so on.
Check out the mod sections of this forum. There are plenty of threads with good projects, some for appearance and some for performance.
Probably a first, easy mod is the "Rear axle vent mod," which replaces the troublesome factory axle vent, and remotes it via a length of tubing to get it above any possible water intrusion. Search for that one, and you'll find both kits from site sponsors and threads on how to get the parts together yourself.
Thanks you toWow, that's a lot for a 2012... but the good news is, there are many folks with Titans with well over 200 kmi on the forum. Great Trucks.
At those miles, you may want to look at replacing the shocks - best bang for the buck is probably the Bilstein 5100's - which will improve the ride quality greatly. There are site sponsors who can get you some great pricing,too. Use the "Forums" pulldown menu and go to Supporting Vendors to see the list.
As my signature says, 2014 Pro4X - just turning 25,000 miles. A youngster by comparison!
Best of luck with the new tuck!