My 2c.
Decommission.
Moisture is your enemy.
Fill fuel tank to top. If you have DCOEs then leave them alone.
Up on stands. Support ute under suspension not body.
Make sure cooling system is full and corrosion inhibitor will last.
Drain engine oil when hot & replace filter.
Fill oil when engine is cold & start engine. When oil pressure lamp goes off run for 10 secs at 2000rpm. Turn engine off.
As Unfamilia says 20 - 30 ml of engine oil in cylinders and turn over by hand 3 or 4 times. Refit plugs.
Remove rocker cover and remove pushrods. Store in oily plastic bag.(yeah I know - pretty anal.) Squirt engine oil over rocker gear. Refit cover.
Disconnect battery, (donate it to someone who needs it unless you can keep it charged) Remove fan belt and store.
Push clutch pedal down. Use a suitable length of timber against the seat crossmember to hold the clutch pedal fully down.
Bleed the brakes so as the replace all the fluid.
Put a rag in the exhaust to seal it.
Tape up air cleaners, breathers or seal air inlet to engine.
Drop windows 10mm. Crack open 1/4 vents. Latch doors on primary latch point to save door seals.
Cover with dust cover.
Good if the engine can be rotated every 2-3 months.

Recommission.
Drain tank and use fuel for mower for the next 5 years.
Put all the stuff back together etc and wind the engine over by hand a few times.
Replace the brake fluid again (yeah I know).
Probably replace battery as its now stuffed.
Fit the fan belt, pushrods (check tappets).
Change the engine coolant and spark plugs.
Start it up and drive it lightly for the first 10 mins.
Realise you were silly to leave your datto for 3 years.
Don't do it again.