It's been 2 or 3 years since I did this, so the memories are a bit faded:



1) Remove screws 1, 2 and 3 with a good philips screwdriver, press firmly so it does slip and round off the slots
2) You may need to loosen the two screws holding the ROM contact bar in place
3) The plastic shroud made sit under the contact bar, but I don't recall the those screws actually going through it
4) The shroud will lift out after that, it won't take much force or pressure, there were no spring clips or anything like that
5) While lifting out the shroud, it's edges with catch on the aperture arm and inner barrel, so you may have to wiggle it a bit.

I know it was really easy and only took about 30 seconds. I'm pretty sure I loosened the ROM contact screws, but remember that not being necessary. The shroud is a flimsy piece of plastic and I think its function is too keep dust and debris for going inside the mechanism. I remember thinking I could take a Dremel tool it is and cut down the shroud so the mirror wouldn't catch. I never bothered. After removing the shroud I did put the 3 screws back into their respective holes. This way I knew I wouldn't loose them, but I also did this just in case they held something else in place. I don't think they held anything else in place, but you never know. I did a quick search and it appears my memory is still intact Just the three screws -

http://www.l-camera-forum.com/leica-forum/digital-forum/24614-leica-21-35mm-canon-5d.html

It sounds like this will work just fine a on 5D too.