The RCD510 will be a straight swap for your standard (im guessing RCD300) stereo in as much as the fit.  You will need a new CANBus to stop battery drain.  I got mine from 
@Eddie-NL on here and followed some online guides for fitment.  The stereo is very easy to fit, again have a look online.  The CANBus is a bit of a pain but definitely do-able.
PS.  This is the exact upgrade I done in my car.   
