Is there any way to open it up and figure out what's going on with it? Any clue on how long of a project it is? The blend door is stuck blowing cold air and I'd love to have heat again

Basically the title. I have a. 2008 Scion xB which I love but one complaint I have is that the 12v outlet turns off when I turn off the key. Is it possible to make it to where I can get it to always be on 24/7? Does anyone have any experience with this?