I just got through going through my speedo and it is dead easy. My instrument cluster slides out easily but you may need to make two hooks from a coat hanger or the like to slide in between the cluster and the dash to help the cluster out. The cluster is connected by an oil line, a wiring harness, and the speedo cable. All are easy to remove. The oil line takes a 10 mm wrench. The speedo cable might need a pair of pliers, no more.

The speedo comes away from the cluster after removing 4 approx. 6 mm screws. A nut driver is handy for this. Unplug the instrument lights and you should have the speedo in your hand. Good time to replace the lights.

The speedo is held to the backing plate with 2 screws. The drive side of the speedo comes away from the dial with 2 screws. This gives you access to the gears (nylon) and the odometer and trip meter. Both are simple but be careful not to take out the small rod that goes across the top of the odometer. This frees up all the cylinders and will take some time to get back together. If there is a problem with the trip meter it should be obvious at this point.

I took mine apart because the needle would stick and then jump ahead. The problem was that a small screw had come loose from just above where the cable comes into the gears and had jamed the magnetic coupling (that is the two metal dishes that trun inside each other). One is connected to the speedo cable and the other to the needle. See that this screw is tight.

Before you start on this clean a place to work so that if you drop a screw you can find it. I don't think that you need to oil anything since the moving parts are nylon. A drop of oil where the cable comes into the speedo might not hurt but I wouldn't spread a lot of grease around.

Good luck