If the drive-shaft is locked like that, it probably twisted the splines on the output shaft (which will need to be replaced anyways)
Is that a t-56 (im assuming it is)?
You should be able to disassemble the trans starting from the front, and I believe that trans uses a two piece shaft (
slide the output shaft and d/s out the rear of the case after pulling off the rear housing)
http://www.allstategear.com/T56Int5.jpg
Take a look at this parts breakdown to get an idea of what I am talking about. Sounds like a lot of work, but my guess is that unit is going to need a tear-down anyways to repair the output shaft.