canon7000d wrote in post #16604422
where do you get that tool from? have looked on e bay does it come with the focusing screen canon wants 300d up front for any repair
It is not a common problem for the mirror to come unglued on the 5D Mark II. That was a known problem with the original 5D, but was resolved with that model in later production and is practically unheard of with 5DII. As others have suggested I suspect it's just a prob with the focus screen frame popped open, and hopefully the screen hasn't fallen out and gotten damaged.
You don't have to have that tool to put the focus screen back in place. It helps, but a pair of standard plastic tweesers will work too. If necessary, you can release that latch with a fingernail (where they show using the tool). You might even be able to use your bare fingers to position the focus screen within the frame.
However try it is best to use a plastic tool or to only handle the focus screen by the edges or, even better, only by the little tab that protrudes from one side. Make sure the frame is open. Place the screen within the frame (or just make sure it's not askew in the frame). Then carefully swing the frame up until that latch on the front snaps it into place.
If the focus screen is damaged and needs to be replaced, it is easily user replaceable and a new one costs $35 (from many sources online). You have a choice of three types of focus screens.... EG-A is the standard one. EG-S is a high precision screen (aids manual focus, with f2.8 and faster lenses), and EG-D screen with a grid to help with composition. The tool you see at that website is included with the Canon screens.
While replacing the focus screen, try not to touch the mirror right below it. It's easily damaged.
If you contacted Canon and they quoted you $300, that was probably for replacement of the mirror. Your description of the problem originally sounded as if there was a problem with that. Now it sounds as if it's only a problem with the focus screen.