00CivicSohc1.6l

Had front main seal and cam seal as well as water pump and timing belt replaced on my 00Civic ex (Sohc 1.6l, non-vtec). Asked them to add 1qt of Lucas stabilizer with oil and I think they added entire 5 qt jug and 1qt Lucas overfilling engine. I checked dipstick and it was over capacity mark! Had them drain a qt when the boss wasn't there. Just so it didn't cause any further damage. The car + engine have 147k + miles. There is a leak comming off of tranny at the bottom, left of the oil pan, where the tranny and block meet. Its definitley oil not tranny fluid. There's a black plate between the two when looking from the bottom of car. Looks to be the rear main seal. Is this where that is located? Any suggestions as to how I should approach the boss at the gas station. I imagine he's responsible for the leak? There was no leak on the left side before repair, only right side below timing belt cover comming off of right side of block before the pulleys/belts on outside of engine. Btw I'm going to have them degrease the engine to make sure this is where the leak is comming from and not anywhere else too/instead. Thanks for your help.