How hard is it to replace the battery on a B8 A4?

I googled it and some people say you have to code the battery?
My battery died and Audi wants 350$ to install a new one. Where I could buy it from parts for 135$. Makes no sense to pay 215$ for someone to just put a battery in :crazy:

 

I found I needed to code the battery and that can be done with VCDS.

Any instructions on how to remove the battery?
I know it is in the trunk but anything special I need to do like keep a power source so the battery never dies etc etc?

 

Should I put an Audi 380amp battery or an interstate 955 amp battery (I'm told it is compatible by a tuner shop that would do the install)


Batteries - Mega-Tron Plus - 85 Months - 765 CCA

 

If anyone interested. I posted what I've done here.
How complicated is it to replace the battery on a B8 A4?