I have seen discussion about replacing missing or failed HDDs on LeCroy scopes of this era before. The conclusion seemed to be that there are no recovery discs for them online, and LeCroy either couldn't or wouldn't provide them. I have a similar LeCroy scope, and the first thing I did when I got it was clone the HDD.
Unless they'll include the HDD, or you find that you can definitely get some kind of install disc, I would not buy that scope.