no you dont have to remove the case...took me about 5 minutes to do. Its pretty self explanatory but here are a few tips.
1. make sure that the glossy side touches the xenarc screen (you have to remove the thin layer of plastic off the nushield protector off first)
2. use a paper business card to stuff the edges inside the case.
here are some pics:
This picture is of my screen installed, with about 5+ months of using the touchscreen (the plastic you see is the wrapping that comes with the xenarc when you buy it new, i never took it off)
This picture is with the nushield protector, looks like there is nothing even on.
I did it all while the screen was mounted on my dash, its pretty simple.