Assuming its a cable driven speedo on ver1, which i beleive it is, then i would suggest you remove the speedo/rev counter pod, very easy to do, put your hand up behind the dash to pop the speedo cable off, you have to squeeze the plug to release it, then remove the screws holding the facia surround then the two screws holding the pod in. Once its out you can go for a drive, or even just push car back and forward to see if the end of the speedo cable is rotating.
If it is rotating then at least you know its not the cable or gearbox, also you will have a converter at the gearbox end this is to convert from kilometers to miles.

I had the c clip come off the cable as it joins the converter wich caused speedo to stop.