Hey Hey
I'm rebuilding a w123 wagon myself right now.. here is the leading info on the SLS
http://www.peachparts.com/shopforum/diesel-discussion/271570-self-leveling-system-how-works-troubleshooting-system.html
Pretty awesome thread! Also I just bought some of the Hydraulic fluid for my wagon. NAPA can get it... If you give them the info for the fluid shown in the above thread they can order the equivalent... some stuff in a grey bottle from Germany...
Have fun with your wagon! She sure is pretty! I think you should put it away and keep it as a summer driver and buy a different car for a winter beater tho!! For Real!