Hi. New to here so forgive me if leave info out.

Car- 2008 Audi A6 Le-Mans
Standerd Audi Concert Audio

I have a problem where I have a parasitic draw and countless times a flat battery in the morning. After about 18 months of constant garage visits. 3 new battery’s, a new alternator and quite a big hole in my pocket. Audi have finally found the problem.... my Amplifier is on its way out and needs replacing.

The question is they are quoting me £800 for replacement and £110 to install and code.
Ive found 2nd hand amp for under £100
can I simply just replace as the 2nd hand amp would of originally been coded just to a different vehicle or does it still need recoding to individual vehicle?

sub note.... if I upgrade the amp will that still need coding or not?

Thanks for any help