This thing is a pain in the berm. Even when it works it often gives a creaking cracking noise and you fear it will break.
There is a clear description in Haynes and even for once some decent pictures.
Basically you have to take out the coin drawer and the ashtray then you'll find I believe 6 other screws to take out. Not in the UK at the moment where my Disco 1 Haynes is, so cannot be absolutely sure, there may be a couple of screws set at 90 degrees to the normal angle.
Then the whole thing pulls out.
The locking device, that locks it in or lets it stay out, breaks for a pastime, but is the same as the one for the ashtray and the coin tray, so you can swop them over. I have tried mending it with little success. Of course if you have a 3d printer, you might be able to copy one that is not broken!
I'm interested "it will not slide back in" usually the opposite happens, i.e. it comes out, will go back in but will not stay in, due to the heretofore mentioned barsteward of a silly plassy locking device.