re doing it the icy veins spell id u gave was right all along. the one i saw on wowhead was wrong.
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I use Glitchy's MES to do spell swaps. Use the Drop down menu all the way to the right. (In image its the picture with the Tools Crossing each other)
Select "Spell Swapper"
Once that menu in the picture comes up Click the "Load DBC"
Then save it as w.e. you'd like. As you see i named it patch-b.MPQ
Then enter the spell id for the spell your using. Then to the right the spell id you want to see instead. in this case
Icy Veins:12472 to Fel Infusion:40396 .. once your done Click Swap.
If you want to do more spell swaps do that before you click Save. As you can do a few spell swaps in the same .MPQ.