Bob,
Do a "Search this Forum" on the Tech Help section. Type in "keyless entry for your 124 made easy". This will bring up a post labeled "I did it! Keyless entry for your 124 made easy". Click on this thread. Go to the second post and click on the link http://www.peachparts.com/Wikka/W124Keyless. There are pictures of how to essentially remove the foam pad and vacuum line fittings for the vacuum pump.
The foam pad is essentially a split piece. Per the picture, carefully split and then work the foam pad out. Next, use a small standard screwdriver to raise the clip for the vacuum line connection. All that's left is disconnecting the electrical connections. Please contact me if you have any questions.

Gilles Kay
gkay737@aol.com