I'm not sure if you can reach it without pulling off the motor mount, front cover, and timing belt.
There is a diagram somewhere in the manual at the below location that will show you how the spring attaches, and you can determine if it is possible to put a new one in without removing that stuff. If I recall it attaches behind the tensioner so my guess is you can't do it.
http://www.floptical.net/mazda/
Have you done your scheduled timing belt service?