Common problem and it wont be the sender on the gearbox, if it were the engine would run like shite and log a code for vehicle speed sensor (Whch is part of the speedo). Now the way to tell for sure is when you drive it if the odometer ticks over yet no speedo the problem lies in the instrument cluster. So take the instrument cluter out and carefully take it apart. On the back of the speedo itself you will likely find burnt tracks on its PCB, if you're handy with a soldering iron/electronics you can bridge the burnt tracks with some data/telephone cable if not any electronics repairer should be able to do that for you (Asiat instruments if you want a specialist). As I said this is quite a common problem and at least on Toyota/Lexus reasonably easy to fix.
Oh if the cluster goes dim(Soarer/SC is good for this as mentioned) they have a flouro tube in them, use toyodiy to find it and the part no and then amayama for the replacement part as local dealers not only want your left nut for a replacement but a mortgage over your house too. First born in some cases (I offered the wife on the last one but there were no takers)
