IIRC the top nut is 22mm or 7/8". I used a deep offset box wrench and you need to hold the shock rod with an allen when you loosen or tighten.

Check the condition of the shock mounts. They might show tears as if they have been nicked by a razor. If they show any wear at all or if they are just old, now is the time to change them. Changing them after you have new shocks on is a real chore.

Many threads on changing shocks without removing springs. That is the way I did it on my 91 300CE. The gist of it is to have the control arm resting on a jack stand ( not a jack) and the weight of the car controlling the spring and keeping it compressed.