Thanks Boyd. I can afford a Montana, but if I can do what I want for considerably less I will for sure go that way. Over on the RZRForum, members all swear by the how great the Nuvi 500 is, but no one can really goes into detail about the mapping works. And trust me, i've asked.
I think the biggest hurdle is finding the trails I want to ride on a particular map product. I assume if (for example) Garmin Topo 24k for MN has the Red Top ATV Trail on it, then I can utilize MapSource to zero in that particular area, cut and paste (or whatever) to make my custom map and then upload it to the Nuvi 500 SD card. I could use the street maps side to navigate the truck to the trail head, disable that, then enable my custom Red Top map and go ride. Right?