you are right. the inexpensive chip is the one you will need. I think it is the Hotspots map. It will do you just fine. To get the MDC spots loaded, you will have to load them on a memory card and trnafer them to your gps unit. If you don't want to use the SD card reader, you could always manually punch in the latitude/longitude of every point. (no thanks..lol)
As far as used ones, I would check the catalog outlet at bass pro.