I am really surprised at all the people saying 'don't worry'.
I am also surprised that the issue of sand is raised as the grounding was described as violent.
If you are willing to take a boat sailing after a mishap like that without a second thought, I for one would never want to sail with you - it is not responsible behaviour. If you are like me (and it sounds like it), it would sit in the back of your mind until you had hauled the boat to see exactly what the damage was. It is insane to suggest you carry ANY of the costs since it is not your boat and since you were not in command.
SO here is my 6 cents worth .... the boat is not yours yet, do not proceed with the sale
until the issue is checked out at the sellers cost. To put this recommendation into perspective, I know of a grounding at around 3 knts where the rock won big time. It cost around 20k to fix this. There was no water
intrusion after the grounding but there were stress cracks in the hull at both the leading edge as well as the trailing edge of the keel. The boat might not have been as strong as the one being discussed here but are you REALLY going to risk that ????
The nick in the keel on this grounding I am talking about would have been a matter of less than $100 at the next haul but because the structure was compromised the repair was extremely expensive and took a long time.
The thing that everybody always mentions when boat buying
- don't get attached until it's yours. You are obviously attached and invested in this boat which is a bad thing. Sit back and rationalize the purchase
.... try to remove yourself from the point where you have already decided in your mind that this is your boat and you have already shelled out money
for the survey
etc etc etc. I know it is real tough to do but that is what you need to do.