This tutorial by dg945 will allow you to create your own main menu (UI). It does go step by step, though you may have to watch it a couple times because it goes fast.
This tutorial will show you how to rig and get in game a custom biped so that it uses Master Chief animations. It is the best and ONLY rigging/ingame biped tutoiral out there, and it is a hard skill to learn. But if its a rainy saterday and your bore