How would I make a player morph GUI?

I have 5 platforms all set up with character models. I want to make a GUI calling on these platforms, in an interface that shows an image of what it looks like, and using the (LeftLeg RightLeg etc.) To replace a players, and after it has done so, teleport them to a platform named BeginningSpawn. It's for a massive game I'm working my butt off on and I really need help. I don't even know where to start.