If it won't work at all, you'll need to disconnect the permanent live for at least half an hour to let it clear itself down - just pull the fuse, there's no need to remove the stereo.
I moved from Pioneer to Kenwoods about 8 years ago when my friend was a sales manager there, and hence I got an awesome discount (and I got top notch tech advice).
Now he is no longer there, I once again have a Pioneer in my gap in the dash - I just couldn't be doing with the down time (and then the time spent re-entering all of my settings etc).