How do you upgrade from Artist to Cubase?

I have been using Cubase Artist 6.5 and decided to upgrade to Cubase 7.5

I could see that in a post issuing the release of Cubase 7.5 there were different payment options dependent on what you were upgrading from. I saw that it was cheaper to upgrade from Artist 6.5 than from AI/LE/Sequel/etc. However as I am in Australia I was directed to a local distributor and on their website it seems there was no option to go from Artist to Cubase. At the time I thought that AI was code for Artist (I was looking for Artist and that was the nearest thing).

It seems I have mistakenly purchased an upgrade from Cubase AI/LE/Sequel/etc that is not compatible as an upgrade - what do I do now?

Question 2 - when I figure out how to get Cubase 7.5 to work, if I uninstall Cubase Artist 6.5 will it stuff things up?