727 - Driveshaft Jammed All The Way In
As for damage.
You mentioned that you had to destroy a u joint to get the slip yoke out.
Was this to get the drive shaft out of the rear pinion with no distance to push it into the transmission?
Which leads me to believe you got the slip yoke out.
Pull the seal off the end of the transmission and post some photos of the yoke and the end of the transmission.