this discussion would probably be better placed in the rcgroups T-STorM32 thread
the answer is either easy or not, depends a lot on the mechanical capabilities at your disposal (I have nearly zero, and it's a struggle)
the conversion consists of two steps:
(i) mounting the ring magnets
(ii) getting the encoder-motor modules (and mounting them)
the first step really depends on your gimbal, motors, and mechanical tools
my simplest solution (which I use on yaw of my gimbal stick) was to just squeeze a chop stick into the hollow axle, and the magnet onto it. For the gimbal in the video I had the (one-time) luck to get someone making me some brass pieces. This step is largely a matter of one's creativity.
the second step is more difficult, as such motor modules are not available. I would be willing to build 3 for you, but would have to order everything, so, that's something about 4-6 weeks (drop me a PM if that is of interest).
maybe you could/want contact rcgroups user buckker for his experience, he successfully did such a conversion. Reading the latest exchange with Ja1012 in that T-STorM32 thread might be helpful too. Pl don't hesitate to ask if questions are still open.