The time it has taken to get your machine fixed is unacceptable, but the more important issue is your loss of data.
Unfortunately I doubt you have an legal standing. If it was critical it should have been backed up. But hindsight is always a great thing.
I'm certainly no expert on this, but I would ask that the drive that was 'literally in flames' be returned as well. It would also be nice to see a report on exactly what happened.
In many years of working in the IT industry I have never seen (or heard) of a hard drive bursting in to flames - or any other component other than a PSU for that matter. It just sounds odd to me.
If the data is really critical to you there are companies that specialise in retrieving info from corrupt hard drives - it's not cheap though.