having just installed Eibachs in a buddies Mazda3 Sedan Friday night I don't know how you can say it is easy? I think this makes it seem like anybody can do it? Which is not how I see it.
Agreed: the backs. They were relatively easy.
Disagree: the fronts. The fact that you have to have some basic shade-tree mechanic knowledge and a few tools that the everyday person does not have I would highly suggest finding somebody who has installed springs on the Mazda3 and ask/beg/bribe them to come over and help.
I have installed springs on 7 of my cars, the Protege5 I have done twice. The setup on the Mazda3 up front is just different than I was used to. Ended up taking 3 hours. 75% of that time was the learning curve on one front and one rear.
My .02 worth