I copy info between my cards and friends all the time. Export all your info you want to your sd card on the 798. Plug that into your computer and copy it to a file.
On the 1198, I suggest starting with a fresh sd card and run all your software updates. shut the unit down, and put the sd card back into your computer. Copy the files or move the files to your sd card. (I like to copy so I have a back up copy of the last 25 years of info) Once its back into the 1198, power up, in the menue, import data. If you have a lot of way points, it will take a few minutes