This is an 100% logic operation and i bet there is a tutorial already.....
What you need to do:
- get monsterfiles(gb/gtx/motion)
- convert into npc files(gb/gtx/motion)
- change filename
- remember filenameprotection - Hex editor (end of the file - change the old filename to new one - of all files(gb/gtx/motion))
3. bones/motion in macrodat.txt
- find monsterlines (monsterinfo -> npcinfo | monsterbone -> npcbone)
Then you should be finish.. I hope I didn't forget anything.
Enjoy and good luck, bet you ll need it :D