Oil Caltex Delo Gold Ultra 6 Litres. Change it after 2500kms along with Oil Filter. Both will cost you not more than 3100rs.
Pajero is an SUV and plus its Diesel. So no worries if u have it washed but remember to cover the open wires if any.
And also DO NOT I repeat DO NOT ask them to oil spray the engine compartment.
Oiling the suspension is necessary after every 2 months or if you are into offroading alot than after every visit to muddy tracks.
Transmission check if there are vibrations or check for oil leakages in front and rear differentials.