If it is similar to the Triton (on which it is based), you can only import samples and keymaps, and even that can prove tricky if there are velocity cross-switched or cross-faded samples in the Akai program.
After you have done that, it's sort of up to you...
One short cut I found on the Triton was, for acoustic sounds like guitar, strings, horns, that sort of thing, you can, after importing the keymap and samples, find a Korg patch similar to what you are converting, and replace the ROM keymap with the new imported one. You will now have envelopes, modulations and effects applied to the new sounds. At this point, it's fine tuning time. Depending on the natural decay of the imported samples, or the point at which they go into a loop, you may have to adjust the envelopes a bit, and depending on whether the import has vibrato sampled or not, the LFO's. And you'll probably find yourself messing with the cutoff and velocity sensitivity, a bit.
It's a pain, but usually FAR easier than building the envelopes and all associated programming from scratch.
But once again, I counsel that this is my experience from the Triton. Your arranger may work differently, I have no experience there...
Have you tried the Korg forums? That ought to be the definitive place for an accurate answer...
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An arranger is just a tool. What matters is what you build with it..!