Disconnect the cable from the speedometer, and move the end so that it is visible from the driver's seat. Does the cable end turn while you are driving? It should spin around... If so, then the cable and angle drive are fine--replace the speedo or repair it.
If it does not spin, then check the angle drive. You can do this, if you are
very careful, by putting the rear of the car in the air, starting the engine, and then putting the transmission in 1st gear (parking brake off) with the engine idling. Look to see if the angle drive moves. If not, then something in the angle drive or inside the transmission is hosed.
The angle drive should just come off; I think the large nut around it loosens and you can spin the drive off?? I forget. The drive shaft inside the rear cover is held in with one very short bolt. Oh, and if you need to get inside the transmission (unlikely), you can just take the rear cover off. That's an easy job; no shims to measure or anything like that.
Before you pull the angle drive, drain the transmission fluid. Or some of it will come out when you pull the drive.
Link to the angle drive in the Bird's catalog:
http://www.pelicanparts.com/catalog/shopca..._pg3.htm#item18--DD