I too just bought a 2012 that had 36k miles on it.
I would recommend changing the oil, oil filter, air filter, and fuel filters unless you know exactly when they were done last. That way you know they have been changed and are on your schedule then. You can get all the filters (Motorcraft) online cheaper than at the dealer. I think I paid $90 for all three sets.
Fuel quality is very important. Keep the fuel filters changed, fill up with good quality fuel, and use a fuel additive like Diesel Kleen to keep the pumps lubricated. Also drain the Diesel Fuel Conditioning Module (DFCM) once a month and inspect the fuel for water. The DFCM is mounted to the frame under the drivers side door.
Keep an eye on the main high temp radiator especially on the bottom drivers side near the drain. They are prone to leaking there. I had my radiator replaced a few weeks after buying the truck because it was leaking. Luckily I had 200 miles left on the warranty! No warranty, plan on a $1,500 fix
The DPF or Diesel Particulate Filter traps soot in the exhaust. After a while ~200 miles the filter will need cleaned. The truck does this by injecting raw fuel into the exhaust which increases the temperature in the DPF to over 1,500 f. This burns the soot into ash which is then blown out (correct me on that last point if wrong).
This process takes about 10 miles and your fuel economy goes down while it's happening. I normally get around 18.5 mpg but it drops to about 12 during the active regeneration.
If the truck is being run hard and the exhaust temperature is above 570(?) f, passive regeneration takes place without the fuel dumping into the exhaust.
The Diesel Exhaust Fluid gets mixed into the exhaust before the DPF in the Selective Catalytic Reduction (SCR). It's job is to lower NOx levels in the exhaust. It's always happening. Usually you can go about 8000 miles before having to fill it up. You'll get a warning on your dash long before you run out.
Hope this helps!