[Closed] Garmin 800 questions

Fairly new to the thing and two issues have come up.
1. I have a cadence sensor on 2 bikes. Am I missing something? I cannot believe that I have to set the head unit up every time I swap bikes. Surely something this sophisticated can cope with 2 sensors?
2. Out today and actually used a downloaded route. At the start it asked me to navigate to the start. I pressed yes and throughout the day the damn thing kept showing bloody great white arrows over the map and point all sorts of directions. Was this arrow trying to tell me the way to the start, even when I was 50 miles away? Didn't do anything as I didn't want to start the trip etc again.
Anyone?