This should be easy eh!
Step 1 = take DJ out
step 2 = take AGG out
step 3 = put AGG in
What could possibly go wrong?

Don't worry - van is on axle stands at the rear and chocked both ways on front wheels.
Engine and gearbox weigh around 250Kg I reckon.
First question - what the best way with these vans to lower the engine and box onto the floor?
A hand winch on some 2x4 timbers over the engine hatch?
A traditional free standing engine hoist?
Oh, and its raining. Bloody typical!