yes the you can get a coin tray, i have one in mine, either get one from renault or somewhere like ebay or a scrap yard.
if you want your steering wheel controlls to work with a aftermarket head unit look at this link
viewtopic.php?f=12&t=8910but why change the radio if you have the 6 cd?? its the cabasse unit and quite powerfull 4x30 watts! just up grade the speakers!!!! alpine head unit is gud but you may end up having to upgrade the speakers to get the most out of it! plus keeping the standard radio you keep the display working also and theifs away!
if your changing the radio to add a amp and sub, you can still do this with the standard radio by buying a Speaker to RCA converter.
if this is ur plan, keep standard head unit and spend the money else where as the box to get the steering wheel controlls to work range from £40 to over £100 dependant on the year of your car and where you buy it from etc etc etc.....................