talk about timing...I just went thru this same senario with my '85 wagon. I could smell a little diesel, but I found drips of brake fluid near the rear drivers side tire. When I inspected the lines I found that salt and such had built up in the rubber mounts that hold the three lines to the floor panel and corrosion had set in. The fuel line is an easy temporary fix as it is a low pressure line, you can just cut it at the leak and slip on a piece of flexible fuel line with clamps until you can get it on a lift and check the whole line. The brake line, however is one that I would not do myself as it requires proper bending of lines to match the contour of the old line. I could not find anyone who sold a brake line already preformed to a W123 wagon so I brought it to the dealer and let them change it. It cost me about $240 to fix the line.
Good luck.