I haven’t seen a step by step guide, but I’ve done my B14s in the past.
1. Get the whole of the rear of the van up on some axle stands with wheels off.
2. Support the rear suspension arms on a trolley or bottle jack. I did this because the springs are still slightly compressed when the shocks are fully extended so helps with removing the shock bolts.
3. Remove the lower shock mounting bolts on both sides of the van. You need to do both sides or the ARB will stop the suspension arms dropping far enough to remove the springs.
4. Lower the jack to allow the suspension arms to drop.
5. Drop the springs and adjusters out.
6. Adjust the rings to suit your new requirements. Rings go up to lower the rear of the van.
7. Reassemble adjusters and springs to the van and jack the rear suspension back up to help align the holes in the arms with the lower shock mounting holes.
8. Bolt the shocks to the lower arms.
9. Remove jack, wheels back on, van back on the ground, job done.