Thank you folks for the help, I think I have straightened this out. As it has been pointed out, the downloaded map can only be used on an individual SD card by itself. There is no way to add other maps to the sd card including Garmin maps that are downloaded directly from their site. Any new download will just replace the file on the card. So you have to put in a fresh SD card for each map you buy from Garmin if you download them. What I want is the ability to have topos and road navigation on the same device and not have to fumble with changing cards on the fly.
It doesn't say when you buy the download on the Garmin site that you have to use a new sd card for each map you download. I called them to see if they would let me upgrade to the DVD version since it was not clear when I purchased and after getting hung up on once (I deserved it) they agreed.
So I had to pay the difference between the lower 49 and the full North America but now I can do what I want.
Thanks again for the help.
It doesn't say when you buy the download on the Garmin site that you have to use a new sd card for each map you download. I called them to see if they would let me upgrade to the DVD version since it was not clear when I purchased and after getting hung up on once (I deserved it) they agreed.
So I had to pay the difference between the lower 49 and the full North America but now I can do what I want.
Thanks again for the help.