Please correct me if I am wrong in my supposition, but from reading your question it appears that you do not have a technical issue installing Visual Studio.
It appears your question is more about licensing and subscriptions.
I suggest that, as you already have "first level partnership with Microsoft", you contact your local Microsoft rep and ask about options available to achieve your upgrade.
As for VS 2012 Upgrade pricing, please read the answer from RobCaron (Microsoft) in this thread:
http://social.msdn.microsoft.com/Forums/vstudio/en-US/84a884c6-c06c-44d0-833a-84d2353a5339/visual-studio-2012-upgrade-price
