Vans are okay driving forwards, as an earlier poster said allowing enough clearance when making sharp turns in tight spaces is main issue, reversing is a different picture, it takes getting used to working just with mirrors, no looking over shoulder when parking.
I do not drive vans that often but do have to every say 5-6 weeks for one reason or another. (Often just garaging one at the end of the day as our van driver could not say get into blocked garage earlier when he finished at 4.00 p.m. (I finish later)
Do remember that delivery drivers are pushed very hard to make targets , deliver quotas, so you will need to be very confident to not get very slowed down reversing in yards etc. Where I work there are about 40-50 parked cars, about 30 different business premises and with at least 30-40 deliveries a day, all of which will need to reverse once into the yard, take it as read that not all deliveries will be pulling into the roadside and then pulling away, a fair number will be working in tight spaces often in reverse.