Oil leaking from rear main seal on 2000 Mercedes-Benz SLK230

My car has a slight leak from the rear main seal and oil pan gasket. It has 100,000 miles and I plan on keeping it. Some say wait until it gets worse to invest the 2500 or so to fix just a leak. Not sure if letting this leak causes any other problems. It is NOT to the point that I need to put any oil into between oil changes,

Asked by for the 2000 Mercedes-Benz SLK230
Is your mechanic sure the the leak isn't coming from the transmission and not the rear main seal/oil pan? I'm asking this because torque converter seal leakage can be confused with a rear main seal leak.