I have a Humminbird 798 and want to purchase a Navionics fish n chip card. I was wondering if I need to purchase the Navionics gold also or does the 798 have enough detail with the factory setup?

I am also wondering if it is possible to transfer the information on a compact flash card to a secure digital card?

Ed, you do not need the gold or any other upgrade chip to use the Fish N Chip with that unit. Just get the Fish N Chip East in the SD format.
I have that chip if you want to check it out sometime to see for yourself the level of detail you get with it. It's just like a topographical map of the bottom allowing you to really pinpoint structure that you may have never known existed otherwise.
I don't know the answer to your other question. It would seem as though you could, but someone with more computer experience than me should be able to answer that.

I just bought a Platimum+ chip for the simrad. The Fish N Chip card is very nice has topo like contours to 1' but does not have all the navigation goodies and photos, info, 3d stuff etc. I was going to get the fish and chip but then opted for getting the platinum initially, then if I need it get the fish and chip. Your situation may be different. The simrad really does not have much of a built in map. Yeah I know it has one but it is very crude. So I opted for the best navigation first. Also one problem with the simrad is that it only has one slot. So I have to swap cards. The plat actually covers the same area and has a lot of the details but the fish N chip goes even further. I will probably end up getting both. Your machine might have a basic built in map that may be "good enough" for navigation so adding the fish n chip would give you the best of both worlds. If you can try before you buy that would be the best!

It probably is possible to transfer the data between cards. (I have not tried it). You will need card readers/writers for both formats or gin up some other way using the computer and the device. The formats may be different if the machines are different so that may throw a monkey wrench in the works. I know ray marine had a user card where you could read/write to from and I used that often and was able to transfer all my waypoints to a new machine but to be honest...I would just rather enter them into the new machine directly. I don't that ***that*** many, maybe a hundred or so tops. I was on a friends boat who had thousands. (a mark for every place he had a hit or a fish !... his machine held 10,000 points.) It would get so covered with marks he had to turn them off to see the chart! My advice is to CALL the customer support line of the company that you wish to transfer the data to. They probably will have a definitive solution or at least an answer.