Advice re new engine

Looking for some advice please…

so we have a 2012 D4 and it has piston slap ? Been advised rebuild or new engine. Until this noise started in the engine we never had any issues, it was an inlet manifold crack which was repaired at the garage, drove brilliant on the way home until literally on the doorstep when this loud banging was heard from the passenger side and the car went in to limp mode. Got it home and recovered back to the garage and it is now piston slap so have been told can scrap it, rebuild or new engine.
We don’t want to scrap it but what else is there to look out for now if the engine is replaced / rebuilt what major things could go wrong . This is the first D4 we have owned, not able to attempt any work on it so really looking for advice please.

I have no knowledge of the D4 engine but can't help thinking that something is off here. All the cases of piston slap that I came across build gradually and do not just announce itself with a sudden "loud banging". I am more inclined to say it's a crankshaft failure but wait for other more competent forum members to pitch in with better input. My advice at this stage is to seek a second opinion.