I would say at this point that leaks happen and continue to monitor the leak.
If you are happy to do any maintinance on your vehicles at all, get an aerosol can of brake clean and crawl underneath the jeep and wash down the area where he says the leak is and up higher on the back of the engine. Then watch to see how long it takes for the leak to reappear. Look at the back of the engine for any other source of the oil too and I know you probably have been keeping an eye on the oil level in the engine.
Just the way you describe how the need for the repair is anounced to you gives me the impression that the shop might be a bit of a repair mill.
JD