Is there an easy way to look for leaks at the problematic points? Going to check out an STS tommorow at a small lot and i want to make sure the case is not leaking.

should i try and look under the engine or feel for oil or what?

Pretty much. I'd be suspicious if it was clean and bone dry - drive it around a little (lot) and then check it. Any grime or buildup can potentially indicate a problem as well. Any oil (obviously) means a current problem.