I did them on my 2001 Hymer B584 and I’m sure they haven’t changed much.
I removed the fixing on the shocks ( star lock washers on mine) with the bed down and then lifted the bed as fair as it would go and I could reach up the side and remove the shock off the back fixing post.
Reverse to refit.
When I took my 2007 B544SL to Peter Hamilton (now retired) he explained that changing the struts on Hymers from 2007 onwards was much more difficult than previously because of access problems. Even took him and his team from first thing in the morning to after lunch.
I wonder if they removed the plastic cover underneath the bed so that they could access the uncompressed strut from below?