You are looking for a W116 chassis manual. They are less common that the W107 (350/450 SL) manuals since the W107 is not only a cult classis, but was sold from 1972 to 1992.
Valve adjustments were required on the M117 engine before 1976, when hydraulic ajusters were installed.
A good vinyl repair kit can be used on the door to fix the cracked spot.
Check for W116 seat covers, they should be available in the usual places. Knowing the chassis type will help.
The W116, while a very nice car, is getting somewhat rare these days. They had a distressing tendency to rust, and the older models with D-Jetronic are harder and more expensive to maintain than the later K-jetronic ones. They are considered classics by most of the people on this forum!
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!