Engine Leaking-running loud--engine light not on

I own a Jeep Wrangler SE Automatic 4 cylinder 2000 it has 80 thousand miles on it. My car is running really loud but the engine light is not on. I took it to the dealersip and after a quick look one of the mechanics said there is a leak coming from my engine and I "may" need work done on my engine----I am afraid because this will could cost me 3 or 4 thousand dollars. What should I do? My Jeep sound like a Deisel truck when I start it up? It is not a Deisel engine.