Use... PANELS!!!
When you click the first button on the side, you can have it like this
[php]panel1.visible = true
panel2.visible = false
etc..[/php]
And you can keep doing it like that, so every button on the side, shows the panels, and disables the button your just clicked, and enables the rest. Same thing i used in my multitool.
Its very basic actually. And simple to do.
EDIT: I saw your Groupbox problem where it hides the rest, what you have to do, is set the location of each of them the SAME, but just paste them anywhere on the form. As long as there in the same location, there not in each other, thus you can do the rest safely, of course, if you modify something and a different groupbox is preset, you gotta move all of them out of the way... blah blah blah.