how to install my european version correctly,while having already the russian one?

[David198502]

hey guys!like some others, i couldnt wait until the release in my country.so i bought the russian version.everything is fine with it,and i even have it in my motherongue.
but i want a physical copy of it,and tomorrow it will be available here in austria in the stores.besides, i dont want to search for a new maddox.dll file after a patch,every time,to have the game in my language again.so i want to install the european version on my rig.
but how do i do this correctly, without having problems with my steam account and the product key.i dont want to mess things up.
i bought the russian version simply to play earlier.now i want to switch to the european.
anyone already did install a european version after the russian successfully?