You don't have to install any apps...it connects to your BB via BlueTooth (built into the BB and the puck) and the any GPS apps on the BB connect to it for GPS info.
You treat it like a bluetooth headset...once you've paired it with the Blackberry all you need to do is turn it on.
After pairing it w/the blackberry, you change one setting in the BB in Options>Advanced Options>GPS to tell the BB that the puck is the preferred GPS source.
Read the review in the thread I pointed you to above.
Amazon has these, I believe, in the $60 range right now, and they have an easy return policy in case you're nervous about whether you'd like it or not.