Krotalus,
No need for the shop to 'Install one" for you........it just sits underneath your sight bracket and is held down by the same screws.
It's such an individual set-up that it would be impossible for a shop to set it up for you ahead of time.
You will need to tweak it yourself.
If you decide on it (and I highly recommend you at least TRY it) get ahold of me, I will walk you through it.
I've set up a bunch of these on my bows and helped others do it properly so I know some tricks.