Having had my cluster in and out a number of times (and boomerang off even more times), this is just my opinion:
You could remove the faceplate 'glass' through the front and replace the gauge faces that way, but I'm thinking that removing the whole cluster with the boomerang in place would be pretty darn difficult. Apart from anything else, getting the screws out and back in would be, let's say "frustrating"! It's difficult enough, even with the boomerang off.
I think it's actually easier to remove the boomerang to remove the cluster, than try to do it the 'easy' way.
Owner of "Campbelle", a Brazen 2008 GXP ... with mods piling up...