I haven't installed the guard you are looking at, but removing and replacing a chain ring isn't hard. I've seen 3 types:

1) Riveted rings: these can't be removed.

2) Rings fitted with allen keys on front and back: for this, you need two allen wrenches that fit the hexagonal holes on the front and back. The chain ring bolts screw into each other. Hold one wrench steady and turn the other one counterclockwise to remove.

3) Rings fitted with allen key on outside and slot on inside: for this type, you need a large flat screwdriver or a chain ring bolt spanner (Park Tool CNW-2) to hold the slotted bolt steady while you turn the allen wrench counterclockwise to remove.