Very gently!

It depends on just which radio is already fitted.  On my '93 Estate
it's a pull-out-and-hide it type but I guess there's not too much
difference.  Usually there are two pairs of holes to the right and left
extremities of the radio fascia.  Insert a 1/8" rod into each hole and
push until you feel the resistance slacken releasing the spring clips
that retain the radio.  You should then just be able to pull the radio
out of its casing.
If not, pull out the ash tray and remove two screws at the top front,
not visible unless you look from under, and loosen one right at the
back.  You can dangle the tray on its electrical cable.  Look from
underneath how your radio is retained.
HTH