Can you fit an EFB battery yourself?

The battery on my sons VW Polo gt has gone.
He has been told he can fit a new one himself by his father-in-law who is a mechanic.

The shop who sold him the battery also says this.

When the battery went on my Golf R i was led to believe you couldn't fit one yourself and you had to have the battery "Configurated to the system".

Who is correct?

Well so far no problems, but if he did within the battery's warranty all he has to do is take the battery back and exchange it.
After all it was the supplier who said he could fit it himself.