WOW! Your truck looks like a photo negative of mine (see my pic). ☺️ Welcome back!
Like you, I owned an Ď05 6.0 liter (see sig). It remained stock except for some Autometer A-pillar gauges. I only sold it because I was ready for a dually.
The only advice I can give you is what has worked for me. I am VERY aggressive about maintenance. I change oil & filters myself (I have installed a Fumoto Valve & I love it) using 5W40 full synthetic oil & Motorcraft filters. I also check the water separator monthly draining about a half pint of fuel into a glass jar. I have never found any water, but t still check.
While I am completely capable of changing the fuel filters myself, I take the truck to my local Ford dealer to have this done because I know the diesel tech there & trust him completely. While the truck is having the filters changed I ask him to thoroughly check everything such as coolant, brake fluid, hoses, belts, brake pads & take care of whatever scheduled maintenance is due. I tell him to do whatever he would do if it were his own personal truck. This has worked very well for me with the two Superduties I have owned.
I also want to mention that my truck is completely bone stock & I intend to keep it that way. I am more interested in warranty & longevity than any gains in performance. As I have mentioned here before, I have towed my 16,400 pound 5th wheel over nearly every mountain pass in the western US & I donít think Iíve had my foot to the floor yet. I would only consider deletes & engine modifications in the event of some kind of failure that required overhaul or replacement.
Once again, congratulations on your new truck. Enjoy the ride, keep smiling & welcome back to the site.
2013 F-350 Lariat 6.7 L PSD Crew Cab Dually, FX4, white platinum metalic tri-coat with black interior, N-Fab step bars, factory spray-in bedliner and 5th wheel hitch, trailer tow package, integrated brake controller, upfitter switches, Sync with My Ford Touch, memory group, remote start, reverse sensing with rear view camera, nav, satillite radio, Weather Tech floor mats, limited slip diff, moon roof, climate controlled seats, engine block heater and tailgate step.
2014 Lifestyle (formerly Carriage) 5th wheel 38' long with 3 slides & all the goodies.
SOLD: 2005 F-350 Lariat, 6.0 PSD, Torqueshift auto trans, crew cab, SRW, short box, FX4, ESOF, limited slip dif., tow command, upfitter switches, 6 CD changer, Lariat Lux. package, camper package, engine block heater, triple A-pillar gauge set (Autometer) with pyrometer, trans temp & voltmeter, MBRP 4" cat back exhaust w/5" dual wall chrome tip, dark shadow gray/ med. flint interior.