How do You Allow Players to Switch StarterCharacter?

I will be as descriptive as possible here because I know I am so close to finally figuring it out.

I have turned off character autoloads because I want the character to become another startercharacter

After I turned it off the GUI doesnt pop up anymore, so if I could figure out how to make the GUI pop up when character autoload is turned of this would help a ton.

After we get the GUI to pop up the GUI needs to have a script that loads the player in and also moves the startercharacter into starterplayer and then deletes the old startercharacter.

I am just so lost on how to do this though.