The timing belt is an easy job, however you do need to take off the radiator and front bumper on some cars.
However there is another chain inside the engine (the name is on the tip of my tongue) which sometimes slackens in high mileage cars (such as my VW Passat) this causes the engine to make a noise it starts of quite and gets louder and then stops its a bit of a cycle. To fix that problem the engine needs some disassembly!