I have done a lot of timing belt jobs on my Miata and my BMW, and I say go for it. It's not terribly difficult, but make sure you get the instructions for it and follow them exactly. Don't try to do things without the proper tools. The tricky part is lining things up. Are you replacing the water pump? If you are not, or you don't have to take the belt off to remove the pump, the cheater's way is to loosen the tension a small amount on the old belt and slice it down the middle the long way while it is still in place and remove the front part of the belt. Now, loosen the tensioner enough to get the new belt halfway on. Then, cut off the rest of the old belt and slide it all the way on, tension it back up, and you don't have to worry about aligning the marks.
Most timing belt tensioners are automatic (spring pressure) and consist of loosening and then tightening a bolt when the crank/cam are in a certain position (off the lobe ramps). You have to be careful about where in the rotation the engine is or you will get the wrong tension and shorten the belt life.
