It is not particularly difficult to drain, just pull the red bung under the van and drain the old fluid into a suitable container for correct disposal. Replace the bung.
Then flush through with water and drain again.
Then fill with the glycol/water mix , then it gets time consuming .
You need to alternately raise the front and back with the pump running to get rid of the air, using the bleed points in the van.
With a workshop doing the change they use a special pump to force the fluid throughout the system and expel any air, and they have the job of disposing of the old fluid.
Just to add a bit more:
You can buy a 12v pump from Ebay for well under a tenner. It simply drops into a bucked of coolant (or water) and forces it through the system.
Couple of short bits of garden hose connected to the flow and return at the header tank (just remove header tank first) will let you not only "force" the coolant out effectively but help to eliminate the air pockets.
One end of "flow" hose into bucket with new fluid ready mixed and other end (return) to a suitable waste container.
(Alternatively first pump through clean water but it's not really needed - 2 and 5 year antifreeze does mix).
Pump new pink fluid through and watch old blue gushing out of the other pipe into the waste container. When this turns pink you know you've done the job.
Turn caravan pump to full and bleed then turn back to number 2 for continued use.
Oh and don't forget the drain plug!!!!!