Idk man my experience was pretty smooth i had some scuff marks and scratches too but they said it's fine it's nothing major..just hope there's no water damage behind the screen only..they said it can have water damage in the back panel but not under ...
Message samsung support on whatsapp that how i got to know if the free replacement is still active or not.. even if the service center denies you can show them the message and they will have to change the Display if your phone doesn't have any major ...
My back also came off and my display got the lines of death but they changed the Display for almost free (500rs labour charges) and with display came the whole casing of the phone and they also fixed the back obviously.