I am sure I don't need to remind you that memory charms are notoriously difficult to completely remove if it is not done by the one who cast it. However this sounds like something of a botched job so there may be some possibility of restoring normal memory function.
I doubt Legilimency would be able to remove what was done but it could certainly give you some idea of the extent of the charm and what damage it has done. From there you may be able to be more precise when removing the spell. It may also be able to identify who has botched the charm. I emphasise the may in that sentence.
Irrespective of that, I should have time to spare on weekends if that is convenient. I am sure Ben has mentioned it but Faustus has gone to stay with Draco for the moment.