If the ring has I think its 3-4 skill mods you CAN change them to others in their catagory.
For example I wanted to check if you could put 5 skill mods on an item, I think it only went to 4, maybe 5, but it was hard to do because when I would pick a skill it would show its replacing a different skill it already had. Skills are grouped. I got it to 4 for sure on an exceptional ring. I think I was able to get music, discord, magery, swords and tactics or chiv.