Changing my headunit at the weekend and hopefully fitting a sub!!!

[MURRAYS444]

As the title boys and girls

I'm hoping to change my standard Audi headunit the double din symphony unit to a single din Pioneer one

I have these parts
Autoleads : Single DIN Facia for AUDI A4 (2004-2008) Symphony - Fully Amplified -

http://productfinder.autoleads.co.uk/productinfo.aspx?&m=AUDI&f=A3&id=57&pID=754

I also have all the cables need for my sub anyone else done this in their S3?

and is it easy?

thanks in advance!