I am considering taking this course to complement my current qualifications (CCNA Security, GCIA, GCIH), however I have a few questions that I am hoping someone can help with.

What do I need to provide, can I use a VM or do I need to have a dedicated system, and do I need to use a specific version of Backtrack or is one provided/recommended?

I am confident about my networking (TCP/IP) skills and my Linux skills are reasonable (can navigate, manipulate files, users, groups, permissions, daemons etc) but scripting is something I have not done a lot of, is this a requirement for the course, if so which scripting language would best reward the time investment? I do understand programming, I write assembly (Z80 and MC68K) to a reasonable standard, but aside from a (very) small amount of C I have not used any high level scripting languages.

Any answers/advice would be welcome.

Thanks.

Yes a VM is sufficient and you will be given a link to backtrack VM image that is in tune with the manual provided.

There are couple of programming exercises but none requires expert knowledge. As you are able to read programs, I believe you will be right at home with the programming exercises. I would suggest python for this course. Learn to write simple network related programs with python. But it really doesnt matter if you choose ruby, perl.
As you write assembly that is gonna definitely help with exploit-development and understanding buffer overflows.
Good luck.

They start with normal unix shell script to do simple tasks, then they use python.

Honestly, the course is very well written, so you don't have to worry about this. It's the easy part of the course! 

I've been recommended this book in a different thread on the site.

http://diveintopython3.org/