Biodome - I'm guessing that you are not yet up to speed on how to find resources on MercedesShop.Com's various FORUMs/THREADs. So:
Let me suggest you first look at the main index page at:
http://www.peachparts.com/shopforum/index.php
more specifically the group of FORUMs titled:
"Do It Yourself Links & Resources"...
"These forums contain links and info for DIY'ers"
and even more specifically the subGroup titled:
General Information
and in this group you will find a THREAD started by me titled:
W123 Vacuum InterLock Diagram
which is more easily reached by clicking on the direct link:
http://www.peachparts.com/shopforum/showthread.php?t=160169
Peruse this THREAD and IF you want high resolution copies of a diagram of the Vacuum Door-Lock system that should be useful to you in troubleshooting your car's system, send me at [email protected] your e-mail address and I'll provide the files. Included is a photo that show how you can use smaller electric plastic ties to snug-up the rubber 3-way & 4-way connectors IF they are still soft and not too loose or cracked.

Now let me specifically ask / make comment :
Q1 - Do you have a "MityVac" or equivalent hand pump/gauge combo?
If not you really need one for this project and as a regular part of your needed tools to work on your car.

Q2 - Is the check valve you speak of the double check in the engine compartment or the single check that is under the dash? Did you check both?

Where you say: "One thing I am having a problem with, is locating the vacuum hose itself I have all the links to hose connector sellers. But no hose." Can I get these at my Auto Zone or Advance Auto Parts Store. If I can is there a specific size that I should get to allow for the correct amount of vacuum to flow through the system." - Let me recommend you find a local foreign parts store. One that specializes in VW(s) would be best and inquire about "metric" vacuum hose. I think you could start with 1 YD/METER of ~4mm ID... but to be sure take a piece of the most common hard vacuum line under the hood with you and have them fit you with what is needed to fit this snug [not at all loose!].

OnLine - Take a look at what our our sponsor has at:
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1WH11JXAQ1WT0T26HE&year=1982&make=MB&model=240-D-002&category=All&part=Vacuum+Hose
which indicates their hose that is 3.5mmID x 9mmOD is $3.82/meter.

IF you are going to mailorder, try to give our sponsor the business.

Regards,
Sam Ross