First to underp2, welcome to the forum.
Buy the service manuals. They are a must if you a DIY.
Or if your going to tinker on your 300CD. You really want the manuals. I prefer the paper manuals but own the CD for the W123. Untill you get your very own copy here is a link to a 300D service manual that you can spend hours learning about your car. IF you have the computer savvy you can copy all the PDF files, put them on a CD and you have your manual, sort of. This is for the 4 door sedan, not your CD. But 90% of it will apply

http://skinnerbox.steaky.org/123_DISK2/program/123-cd-index.html

A link about the cars, different body and engine types.

http://home.hiwaay.net/~gbf/mbmodels.html

300SDLLLL
Ok somewhere in the service manual I am directing our new member to get. there is probably a job number for lubricating the cables in the car. But I have not recalled seeing it. How do you lube your cables? What lubricant do you use and how. Should I lube the 240D AC cables, idle adjust cable and hood cable? 300TD does not have the first 2 so I'm new to this area ( and I haven't done my 300TD hood cable, don't tell anyone). Your input would be appreciated.

Dave

__________________
1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car

For new members.
Do not get caught with a hood that will not open.
Hood cables go bad, latches need lubrication.