When you search for you spell on WoWhead, grab the ID from the Specialization tab, then look for the tab named "NPC abilities".
where are you finding the spell ids for these? want to do same for warrior but not sure where to find them
You'll see several spells with different icons and what not, it's just a case of trying each of these abilities until it you get the animation/sound you want. For instance, my Crimson Vial spell is replaced by the NPC ability "Druid's Potion", which is used by Muyoh in the Wailing Caverns instance. That's the process I used to change my abilities using Tmorph.
From what I've seen, you're much more likely to get the desired change from the NPC abilities that have a level requirement, and are at the top end of the tab.