Timing belt replacement varies greatly between manufacturer and engine. Outside of visually inspecting the belt for obvious wear and cracks, there is no way to no it's on it's way out until it snaps and then you're SOL. If the tensioner's locking up you may get warning noise from it before it takes the belt out. Bottom line, don't play with it, expensive engine damage will likely result if it fails. Consult your owner's manual or look it up online and don't exceed the recommended mileage/time interval of replacement. Not worth the cost.
---------- Post added November-21st-2011 at 09:54 AM ----------
Ren, send me a PM and I'll get you in touch with someone. A good friend of mine for over a decade, and probably the only person other than myself I would trust to work on my car, is the only tech at a small shop is Silver Spring. They have very reasonable rates, he knows his stuff and is honest.