1997 Grand Am leaking oil

My 97 Grand Am SE 2.4 seems to be leaking oil underneath the front end. I have not been able to find exactly where it is leaking however. Oil pan? The car has 87,000 miles on it, but shortly after I bought it 3 years ago the engine threw a rod. Luckily I purchased an extended warranty. The dealership put in an engine from a wrecked car. They ended up having the car for 4 weeks, because they kept having problems with water pump? Any help is appreciated.

Thanks Eric

a possible culprit could be the crankcase seal. Check the accesory end of the engine down underneath your flywheel.