This is a simple tutorial on how to add skins to a unit. You click an ability on the command card for an SCV and then you get a probe... they will have the same abilities and stuff, it just looks different on the outside.
In this tutorial we shall allow a SCV to change his "skin" to a probe.
Requirements: Must know how to naviagte through the editor
Part #1 - Ability
1. Open up the Data Editor
2. Create a new ability and call it "probe model" (just an example, you can call it whatever you want).
If this unit is supposed to revive and/or all unit of this type should look identical, I think using the same method as upgrades use would be better: When upgrade X is researched, all current and future actors will have the new "skin". Just take a look at the zergling with metabolic boost or the dark protoss.