Instructions
Start "Starcraft II - Map Editor" from the start menu. The program is located in the "StarCraft II" folder.
Load the map you would like to edit. To do this, click "Open map" from the "File" menu on the top toolbar.
Double-click on the unit you would like to edit. Its properties and technical specifications will open.
Click the "Model Linkage" tab from the top of the window.
Double-click the "Actor" field. A list of units will appear.
Click on the file of another unit to change the unit's model file.
Press "OK" to finalize the change. The unit will now have the appearance of the unit you selected, but it will still retain all of its previous statistics and abilities.