Hope you get a good result.
I had a similar problem when my A900 failed earlier this year.
Last November (2013) the actual mirror detached from the frame holding it - I sent it in for repair with Sony, and had it back in ~2-3 weeks.
It got used for my Iceland trip in March (1000 shots?), but in May failed again with the same problem.
Repair centre were helpful, but I had to pay for the repair and apply for a refund once they had the camera and could confirm themselves it was the same fault.
They duly confirmed the fault was the same, and this time they would replace the mirror assembly (rather than just re-glue the mirror, which is what I assume they did the first time).
Customer services then point-blank refused to refund the second repair fee, as it was outside of the 90 day warranty on repairs!