1) Note the orientation of the cap.  In the picutre above, you can see the vent in the upper right.

2) Using small flatblade screwdriver or pick (you may need more than 1), gently pry under the cap to release it from the snaps.  Do not break the cap!

3) Once the cap is off, under you'll see the diaphragm, a plastic support for it, and a spring.
4)  Here you can see the tear in our test car diaphragm causing a vacuum leak.
5) Place the plastic support in the new diaphragm and into the cap.

6) Place the spring into the housing.
7) Snap the cap back into place with the same orientation as you remvoed and you're finshed!