With the image importing, how far did you get? Can you paste the exact code you tried in the listener here? Or maybe screenshot after you've typed it, showing the error? I think it could be like as simple as mistyping something but I'm not sure.
If you're following the steps you linked, I'm assuming you were able to make a dithered gif of the right resolution? I think once you've done that it should just be as simple as running just this one line in the listener
card.image.paste[read["image"]]
and then selecting the gif.
Or did you have issues earlier, exporting the palette out? Using this code?
r:image[16,1] each c k i in colors r[i,0]:c end write[r]
From the looks of it this should be safe to try running one line at a time in the listener? Then we can see where you're having issues.