Inside the fridge you should be able to spot some pop off plastic covers around the side edges and maybe some on the rear wall. Pop these off with a small flat blade screwdriver and remove the larger screws behind them that hold the fridge in the frame.
Take off the bottom vent cover outside the van and disconnect the gas feed pipe. You should now be able to slide the fridge forwards.
Can help if you have a mate push from the rear as you pull from the front as they can be a tight fit