Do you know where I can get a 300D 1985 Turbo sedan timing chain kit that includes everything (except the tool),gaskets to replace those removed along the way, even literature, instructions, documentation...
Or is the Timing Chain plus the "closing link" really all I need?
Where is the best documentation--the service CD?, the Mercedes hard paper manual?, the Haynes manual?

all you need
 

is the timing chain (it comes with the link) the valve cover gasket, a new tensioner, the tensioner gasket, the crimp tool and some time. I would recommend having a side grinder (or something to grind off the old chain link) a really strong light (to look down in there and inspect the guides) and the socket to fit on the crankshaft bolt to turn it over with. Make sure you stuff clean rags down in the space underneath the cam sprocket to prevent debris from falling down in there. Also, after you remove the valve cover you will want to remove the tensioner. Start everything at TDC and with the new chain in place you should end up at TDC with the cam marks lined up. Oh yea - use a magnet to remove the debris prior to pulling the rags out and make sure you maintain the chain/sprocket relationship at all times.

By all means - if you do this job yourself - take your time.