Let me help you all clear things out abit.
From what I have heard on other forums, Ee ground glass(focus screen or whatever you call it) can be inserted into the Eg slot on 5D2.
Clearing things about how ground glass works, basically a ground glass is a rough surface for image to be projected on for preview. The a finer grain surface allows the ground glass to display a closer representation of the image on the final output at the cost of transparency.
Canon Focus Screen:
Ee-S, fine grain, less light can goes through since the screen "absorb" them, however subject in focus "pops" like what you see in low depth bokeh pictures. Unless you have a serious night blindness and shooting at places that your camera cant focus, EE-S will do just fine with any lens other than F8, lol.
Ee-A,Ee-D, much more translucent, meaning more light can be pass through the glass and you see bright bright picture, but is harder to judge focus since it does gives a wrong perception of depth. Basically Ee-A focus screen... I would say just treat it as a view finder, do not expect much from it, it is usable but once you used Ee-S, you will realized Ee-A is ****.
LIGHT METER is affected by the type of focus screen as it sits behind the focus screen at the prism. Setting the correct screen type in CFn is important for accurate metering, that is why some split focus screen makes your center point wonky and requires compensation of -1.
AUTO FOCUS is not affected by the type of focus screen as it sits below your primary mirror.
Might have some mistake as I am rushing this post for dinner, correct me if necessary. =]