First: why do you want to?
If it gets too grotty, I occasionally scrape off any really crusty stuff with a plastic putty knife and then rub down the walls with paper towels or rags and Real Lemon lemon juice or its store brand equivalent. Cleans it up, doesn't remove the seasoning, and the lemon juice is completely non-toxic: at least that's what the manufacturer says. I use it to clean the bottom after each smoke too. Forgot who recommended it to me ,but thanks.
If you do clean it with a power washer, you'll probably need to re-season before you use it again.
I don't think you'll get in to the electronics because they are all up top and out of the box.
I've been into my AmeriQue to change the element and there are no electronics behind it either.
Just so you don't drive any water in to the insulation and potentially cause a
short (although that sounds like a very long shot)I'd go easy around the element anyway.
Hope this helps.
Hook