You will need release keys to pull the radio (very cheap from ebay or a
car audio place) and the unit itself will come apart pretty easily with
the appropriate Torx head screwdriver ;)

IIRC you will only need to release 2 screws from the upper-rear edge of
the standard unit to pop the top off, and this should be enough to get
the coins out.

Try to avoid shaking the unit around too much when removing /
dissasembling it... there are bits in there you dont want to scratch
with a coin ;)