Engine Funny Noise problems of the 2010 Toyota Prius

My 2010 Prius has relatively low mileage - approximately 44,000 miles. It has been routinely maintained at the dealership where it was purchased new. I just replaced the tires a couple of months ago, and the only issues have been the takata airbag recall & the need to replace air filters more frequently than may be normal because I do not have a garage so it is parked outside in a driveway where exposure to pollen & debris from trees is excessive. After a significant wind & rain storm Wednesday night, the engine rattled & made unusual noises for several seconds when I started the car. Then, the "check engine" light came on. I checked the manual, which said not to drive & to call a dealership immediately, which I did. I was told it was not safe to drive & it should be towed to the dealership. I waited until the following morning & started it again to verify the check engine light before having it towed. After I was at the dealership for 3 hours, the service guy told me that when he started it, the car run fine, the check engine light was off, & they were not sure what caused the problem, but their diagnostic evaluation showed a problem with an oil leak in the head gasket. I was quoted a cost of approx. $1500 to open it up, fix the leak, & check for any other problems. I gave the go-ahead, but am wondering if this is symptomatic of a greater problem that will be repeated. I am waiting to hear back from the dealership after the repair today. My goal is to drive the vehicle until it has 100,000 miles or so & then trade in for the newer model. Did I make the right decision? do I have a lemon? is this a common problem with the 2010 model? is it reparable, or could the engine now be warped and irreparable?.