Best thing to do is get a shop manual specific to your car, preferraby published by Mazda, and not a third party. That will provide you not only how to info, but all specs (like torque) and tools needed. You will need something to lock down the camshaft(s) so they don't move when replacing the belt. If your water pump is located under the cover with your belt, you probably should replace it as well so you won't have to tear the engine apart a second time to replace it. (Standard procedure on Honda's, don't know about Mazda's). I have done the job on a Suziki Tracker twice, not a major job on that vehicle, and once on a Subie, again not a major job. Neither of those vehicles required replacement until over 100k miles.

With a little skill you should be able to get it done in a few hours.