Honda Repair: Transmission speed sensor, engine vibration, speed sensor

Question
I have a 91' Honda Accord LX 4 door automatic. Diagnostics tell me I need a transmission speed sensor.  Where is the speed sensor on the transmission?  Is it a cable?  I have replaced the AC compressor/dryer & o-rings so I feel I am fairly capable to replace the speed sensor.
Also, I have alot of engine vibration when idleing in drive.  Is it due to bad engine mounts?  If so, how do you replace them?
Thanks.  

Answer
Ron,

I am not exactly sure which sensor you need. Is it a Vechicle Speed Sensor or a mainshaft speed sensor. I would guess it is your VSS since I have seen them go bad often. Is your speedometer not working? It sits on top of the transmission in the back towards the firewall. It is electronic. Unplug it, remove the 2 10mm bolts holding it down, lift it up, (watch out for the small piece inside the sensor. The new sensor comes with a new one) then install the new one. Not to difficult to replace.
As far as a vibration goes, you need to check all the motor mounts. They all break within time. You need to buy a manual in order to learn how to replace them. For me to explain the replacement of all your motor mounts would take me far too much time here.
Good luck.