855 & POI's, etc.

 

I am awaiting my new Nuvi 855 and have some questions. With the millions of POI's in the unit, how do I know which ones I should install. Do I have to navigate through them all or can I safely install what may be a duplicate and let the Nuvi recognize if it is or not. Will it tell me it's already installed?
What about Garmin Roadtrip? I tried importing my old waypoints in GPX format but Roadtrip is telling me it can't. Any ideas?