There's a guide on here on how to upload pictures ;)
If you have a 6CD changer in the armest then your laughing, it's a simple box change there and plug and play will take 5 minutes max! That will be you full ipodded up then (is that a new word?)!
In regards to the RN 510 it is truly top notch but i opted for the RNS 310 instead, it;s exactly the same with a slightly smaller screen and no internal hard drive, however it has the option for an SD card. I paid around £300 for my head unit brand spanking new off eBay, that included all GPS adapters and everything. I had the gold 3 weeks when I got that and fitted it myself within no time at all.
Might be an option to look at? I didn't need to change my CANbus either (this is needed for many cars that wasnt the RNS510 upgrade)
Hope all this helps, but if you have the CD changer then the iPod is easy, cradle should be removable and then you should be good to go!
Simon