First of all, fix your grammar. I can understand some, but please, take some lessons.(or it's just natural with your country, I can't tell.).
So, you are telling: When you change the model of the doodad tree (ashenvale) and the model is not working? Are you sure you imported all the textures needed? Did the creator tell some custom paths? I can't tell.
Hope I helped
-Da Fist-