agjil

I believe the retrofit can be done both on premium plus and prestige.
You would have to purchase the parts and either install it yourself or ask your dealer or a 3rd party for help.
Audi dealers will probably charge more for the labor than 3rd parties.

agjil

Surround Camera Retrofit [4G8SRDCAM] - $2,895.95 : OEMplus.com, Original Equipment
It's not cheap, but costs less than selling and buying a new car.
I guess it will come with an installation manual, but it's probably best to contact the seller directly.
Also, I've seen periodic discounts on this website, so you may want to wait till the items are discounted again if you're interested.