Yes, straight fit but you need to find somewhere to mount the GPS receiver. Most people tuck it up into an area under the top vent.
Aux port connects into the big block connector at the back. Google it.
Google 'RNS510 nav maps' and there's a tonne of info, ranging from legitimate DVDs from VW for approx. £30, to dodgy copies on flash drives. Take your pick.
What revision RNS510 did you get? There have been dozens of updates (suffix letter on the part number) and if yours is old, it might need a firmware update.