Rear speakers & Aerial amp - Mk1 Octy Estate

Hi all,

I have a Mk1 Octavia estate with only the standard two front speakers - this model did not come with rears. How difficult is it to fit speakers in the back - is the wiring going to be there already so that I can just connect speakers or will I have to run wire back from the headunit loom? What are the required dimensions of speaker for the rear?

One other thing - I'm getting a Blaupunkt

Melbourne SD27 head unit from Bluespot - Blaupunkt Melbourne SD27 - perfect for me as I hate carting CDs around. I have purchased the ISO loom adapter and an aerial amp. I know that this has been covered before, but what is the procedure for connecting the power wire from the amp to the headunit? Do I plug it into the ISO adapter somehow?

Sorry for all the questions and thanks in advance for any help - as you can tell, I am not very clued up on this.