Do I need a front door on it or not?
It's a lot easier to get to your PC from the front than from the backside, IMO. Door or drawer, your choice. There are also numerous examples on this site, like the one Sprucemoose posted, of where they removed the components from the CPU case, if that's your thing.
Can I program my IPac to completely run the machine from just my Control Panel?
Depends. I use a trackball and two buttons on my CP as the mouse and works very well. I have an Imperial PS/2 trackball but the Happs work fine, too. You can perform most Windows functions with just the mouse. Installs generally require (for me at least) a keyboard. I built a keyboard drawer, but find it less necessary than I originally thought. As long as you can get to the keyboard when you need it, just keeping it on top of the CPU case might be fine.