Q1: Any Kingstone SDHC (4-8 class) card work well on my Nuvi 765 for example! The best value for the amount of 16Gb today. I of course have limitation in 4Gb for first and second map on card (8GB totally) but I need in addition space for 3D.IMG and JCV files and so picture and POI.
Q2: If you remove the SD card with maps of course maps in the device will not be! Nuvi work with only a memory card inserted into the device. If the card in your pocket is not serious to wait what Nuvi read it
Q3: Basecamp, MapSource, MapInstall and HomePort is actual program and work fine if you know what you want to do with its.
Q4: Stupid question because you have not done anything. Try and then ask!
Q5: Only JCV will work on your Nuvi. D3060070A.JCV is suit for you. But not at all intersections is in it. Be realistic!
Q6: If you do it as written in this forum so it is no doubt in success. Have problems - ask!