The MG now has a speedometer cable that works. I believe the last time it was useful was when the car was being towed by a truck. The Northwest Import family hooked me up with a nice pre-oiled speedometer cable. The removal of the old cable was fairly straightforward. Unscrew the union at the transmission, which required vice-grips to get loose, and unscrew the union on the speedometer itself. Run the new cable and voila.
I have become fairly adept at removing the gauges so I am sure that helped. While the gauge was out I also hooked the trip odometer up which will be very useful while determining what kind of mileage I am getting with the car. I did have to remove one gasket in the firewall to get the old cable out and the new one in. I didn't have a new gasket and could not salvage the old one so I used several loops of repair tape to seal the hole back up.
Overall, the job took about 3 hours which includes the time to get the tools out, do the job, clean the tools, and put them away. Don't forget to unhook the battery before doing this job as your hands are behind the dash near many wires.