To remove the broadcast radio (stereo) from the dash, you need to acquire a set of radio removal keys.
these are a pair ( and you need 2 ) of " U " shaped wires of about 3mm thick. they have a groove machined on the ends (both) about 1.5 mm from the end.
to remove the radio you need to carefully insert each key into the pair of holes in the face of the radio. preferably one at a time.
you will feel (as long as your not rough) the key engage the groove into the locking mechanism. with both keys engaged, move the top of the keys apart, you should feel a bit of a click.
The radio should now slide out. Disconnect the antenna connector and power,speaker connectors.
If you damage the locking mechanism of the radio by poking any old thing into the holes (and you will break it if you stick any old thing in) then you will have to destroy the radio to get the remains out as the escutchion (the surrounding) panel has 4 screws behind the radio. you cant remove the escutchion without removing the radio first.
As for fitting something else into the hole,, its easy enuff if you have the skill and patience to make or modify the brackets.