Get a Harbor Freight Catalog, (they are on the web) and order a $5 Mechanics stethescope. I have had one for years and use it all the time. It will come with an 18 steel probe that you can place against the different parts of your engine and it's accessories and listen to tell where noises are coming from. Most noises are from bearings going out in accessories such as your alternator, power steering pump, or water pump. By placing the steel probe on each accessory you will hear the noise quite clearly.
Also, if you pull the probe off and replace it with a couple of feet of some 1/4 tubing you can run the tubing around your engine compartment and listen for exhaust and vacuum leaks.
Don't panic. Most things that wear out on a car are designed to be easy to replace!