This instruction will show you guide on how to change the engine oil at home for Mercedes GLK.
This is same topic article for your further reference:
How to Change the Oil on Mercedes Benz GLK350 4Matic

Steps:
Use a jack underneath to lift both the wheels off the floor (you can also do the oil change on the ground)

Unlock all the bolts then take the engine cover off

Oil drain is right there , unlock the 13mm nuts

Put a vessel under the oil drain, Leave to drain while changing oil filter

Take off the engine cover,then remove oil filter housing

Replace three O-rings and filter

Put it back in position

More cases about Benz, please refer to Benz Trouble Repair.