I think that there is an L-shaped bracket which fits underneath the turntable light, and holds another metal plate, which has the light on it. The L-shaped bracket is secured by a screw to the underneath of the turntable. So, to access the light, remove the platter and mat (take care not to scratch the magnetic tape on the inner rim of the platter), followed by the dust cover and hinges, and then remove the base from the bottom of the turntable (quite a few screws hold it) to gain access to the innards. Then from underneath, remove the screw (it's the one closest to the front underneath the light) holding the L-shaped bracket.
Once that screw is removed, the L-shaped bracket, with the light and plate attached, can be lowered down from underneath the turntable, leaving the plastic housing on top of the turntable. You may have to move the light assembly and bracket slightly rearward to clear the housing when removing the light, before you can lower it down, from what mine looks like. There is also another screw underneath, just to the rear of the L-bracket screw, which holds the plastic housing assembly to the top of the turntable – that also may need to be removed, or loosened, to allow the lamp to be removed from underneath. Once you have the L-bracket and lamp out, another horizontal screw holds the light bracket (metal plate) to the L-shaped bracket.
The above came from my post over on audiokarma about how to gain access to the light for replacement.
The lamp itself is designated PL601, Sony part number 1-518-421-00. Whether that part is still available from Sony, I don’t know. However, the lamp itself should be easily substituted by (for instance) small car dashboard light globes, or similar 12V lights. It’s a 14V, 50mA lamp, but Sony actually run it at just under 12V, because it’s in series with a 47Ω 1/4W fusible resistor, which drops slightly more than 2 volts from the -14V rail.
Sorry to take a while to answer - I only occasionally get over here. Good luck!