Teeny Tiny Tutorial
You don't need a new model for that. It can be done with a simple trigger! Here is a teeny tiny tutorial:
1 - Open Object Editor
2 - Create a unit, and set name, hp etc (this unit will be the statue, so the model should be Arthas)
3 - Set the color of the statue to the color you want it to have (light grey is the most used)
4 - Place your new statue somewhere on the map.
5 - Open Trigger Editor
6 - Make a trigger and name it
7 - Create a new event, saying Map Initialisation
8 - Create a new action, saying Animation - Set Statue animation speed 0% of it's normal speed.
Voila! If you can't model, this is the best way to make a statue.
PS: This technique only makes the statue ALL grey. If you want it to have details, (leaves, dirt etc.) you can either model it like you said, or skin the Arthas model, using Warcraft 3 Image Exrtactor II or Warcraft 3 Viewer to export the skin file. You will also need a program that can paint .TGA files.
If nobody want to make you this model, you should use this technique.
Thank you for your time.
•Goku-X