Well....you say they just replaced the clutch...so the damp spot in there is probably just a worn or slightly damaged rear main seal, I wouldn't worry about that as long as it isn't leaking alot of oil.

Back to the noise. I wish I could hear it for you and help you trouble shoot it, that would make this easier. In a Jeep you sit on top of everything from the engine to rear axle so the noise could be anywhere. Check the brakes, could be something there. Jack the front axle (both front tires) off the ground and cycle the steering, maybe there.

After that stuff we may have to start looking at difficult and expensive stuff. *****