When I replaced the radio in my 07, it was a permanent install unless you wanted to remove the dash. I drove around for about 6 weeks with the radio almost locked in, but not all the way locked in. I wanted to make sure that everything worked perfectly before pushing it in the final half inch. I believe the 04 will be the same way. Make sure everything works as it should and that you are happy with the radio because once you snap it into place, it is going to take a lot of work to remove it.