I've done starters on both turbo and non-turbo 300 d's. In neither instance was disconnection of any suspension component necessary. The wheels must be turned one way or the other to get the starter out and it does not come out in the same place on the turbo and NA but no disconnection is necessary. If you search on my posts I describe somewhere the exact space the starters must go thru on each model.
Also, in an old thread, someone described cutting a hole in the firewall to access the top starter bolt. I considered doing it but tried the long extensions and the bolt came right out. If I was having trouble, I'd cut the hole and put a rubber plug in afterwards.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13