Changing blizzard animation with WinMPQ

How do I go about changing it with WinMPQ? A step by step would be good. Then maybe I could try doing the same with different spells, and learn more. So far here's what I've done, and it hasn't worked. :(

Found the blizzard target anim file. Extracted it. Replaced it with an arrow target anim model. Imported the new extracted file into w3x map. Casted blizzard. No animation. Not even one ghetto arrow fireing at the person while the whole group got a blizzard effect (what I suspected *might* happen)

So any help? What am I doing wrong?

Lets say you were trying it the hard & wrong way.

1) Extract the file Units\HumanAbilityFunc.txt from war3patch.mpq

2) Edit the model link in the buff art for the Blizzard spell (a buff has the same code as the spell, but with a B (most of the time) )

3) Inport the edited file in your map with the Import Manager

4) Make sure you use the custom path : Units\HumanAbilityFunc.txt for the imported file.

Regards