top to bottom inspection, address any leaks. Complete fluid change; engine oil, transmission(not flush, just drain and top off), differentials and radiator cant hurt. Cant hurt to do an oil sampling and pull off the turbo boot to see what shape the compressor wheel. those two things will give you a good idea of the kind of life the engine has had and how much it has left. I would definitely use synthetic oil for it.
AS for upgrades:
If your going to be towing heavy/fast/hills you will need a trans cooler: I suggest a Tru-Cool
Gauges: EGT, Boost & Trans temp
Tymar Intake with turbo back exhaust.
Later on you will probably want a chip with some tow/fuel economy tunes
And if you are towing heavy you will want a TBC - suggest prodigy 2 or 3