So I saw Ghostnovas old [Tutorial] SC2 kitbashing in 3dsmax. So I decided to try som 3ds max.
I have successfully imported a presever and Zeratul. Then I detached Zeratuls "mask" and tried to put it on the presever all according to the tutorial.
But I have no bones to pick from, I can pick "display all" but that dosent work either. I then tried to add/update bones, but no succses.
Now you have to remake model's materials. M3 exporter has different material format, it's not compartible with Art Tools. But all you have to do is create a sc2 standard material and pick the diffuse, normal and specular textures for the respective material's maps. If you will have any troubles with it, check Art Tools docs, it has a nice Materials tutorial.
Animations format isn't compartible either, so you will have to open animation floater of the art tools and recreate the anims there (for it, you need to write down their names and start/end times, but remember: import with 30 fps, not the default 1000)