You only need g15-3 (g1-3) for the guide, the maps are on any DCII premium distribution feed.
Also if you do get a used system ask the owner to load the latest maps, with a 920 they would need to go do a unplug replug on any channel with map data, the 922 and 905 will just need to be tuned to the proper channel for a minute or two.
Also if you do get a used system ask the owner to load the latest maps, with a 920 they would need to go do a unplug replug on any channel with map data, the 922 and 905 will just need to be tuned to the proper channel for a minute or two.