Speedometer/odometer stopped working

After my speedometer was jumping all over the place on a drive this last weekend, I took it out today and realized the speedometer and odometer were not working. I did a search on this problem and found this post by aaronm from back in November of 2008.

http://www.ferrarichat.com/forum/showthread.php?t=220854&highlight=348+speedometer

I think it may be the same problem because both the speedometer and odometer went out at the same time. I checked in the speedometer console "pod" and didn't see anything obvious with wires or connections so it leads me to believe the sending unit is bad. Two questions:

1. If the sending unit IS bad, is there any way to test this to make sure of it before I order a new one.

2. In the old post it was mentioned that to replace the sending unit you need to drain the gear box. Is this correct?