If the headlight and front running lights are on, the speedometer should be back lighted. There are three screws that mount the instrument panel to the fuel tank. When you lift it, you need to put something under the panel to keep it from scratching the tank while you undo the speedometer cable and a couple of electrical connectors. Once the panel is off, it should be straight forward to figure out how to replace the bulb. I've never replaced that bulb, but taking off the instrument panel has to be done to pull the fuel tank and I've had to do that many times.
Same thing happened to my 2004 1100 at around 12K. Shop fixed it for like 10 dollars when I had it in for oil change. They said it was no big deal to do and didnt seem surprised at all that it went out.