I noticed there were a lot of people still having trouble doing mount model edits even with very clear guides, so I made a simple-to-follow video. If you can't read the writing in the video, view in HD here. Although I may be doing it slightly differently, I would not have properlly learned how to do this without ~sInX's guide.
Download Links:
WoW Model Viewer
MyWarCraftStudio
DBC Editor
Edit: Was requested to also make a tutorial on spell model swapping, will make it soon.