The accelerator pedal is a bit of a distance from the oil pressure gauge on the W123. Are you certain the gauge is the source of your leak?
Its possible the vacuum pump's diaphragm has ruptured, allowing oil to contaminate vacuum lines and hoses that supply, among other things, the vacuum switch (attached to the ignition lock) that controls engine shutoff. This switch is closer to the accelerator pedal and may be the source of your leak. I've seen these drip oil over time when the vacuum pump fault is left uncorrected.
Pull your instrument cluster (use M-B's pulling hooks or make your own) and inspect the back of the fuel/oil press/water temp instrument cluster. If the cluster is dry, the gauge is not your problem and you will need to look elsewhere for the leak. The cluster can be pulled without having to remove the lower dash access panel.
Have never seen a supply hose failure; oil loss at the cluster is typically due to a loose nut (10 mm) that connects the hose to the gauge. Additionally, the oil pressure gauge has a diaphragm that can rupture; in that case the cluster will need to be replaced.