oil leak

I have a 2005 Ford Explorer Sport Trac in excellent working condition. I recently had routine maintenance performed (oil change, brakes, etc). Following the work, I discovered oil on the floor of my garage from the passenger side of the truck. I returned it to the service department and they told me I needed to have the rings replaced on the motor, a very expensive thing to do, especially when it was not leaking before the work! They said everything else was fine with the work they performed. Any less expensive suggestions before having this done? Thank you!!!!