The integrated RD3 radio/CD player is a good radio; nonetheless some try to replace it with a later head unit. Adaptors are available to fit later head units and retain the remote read-out and controls. Personally I can't see the point as the existing receiver is well up to the job in (let's face it) cars that are now (December, 2017) mostly ten years old.
This would have cost £1,020 back in 2006
The original Sat-Nav firmware on my yellow car was version 5.42 and worked well, though the Sat-Nav information dated back to 2005. To update to the Sat-Nav 2013/4 discs required a firmware update; these are occasionally available on ebay.
The RT3 Firmware was updated from 5.42 to 5.95. With the engine running to prevent the car going into economy mode, insert the update disc and leave it to complete the update. It took only 2 mins to load files and 6 mins to load Navigation approx. It did eject and auto-reload several times. Left it running for 15 mins to be certain and there was no further action so assumed all was loaded.
The update in July 2014 reset many of the settings, so I had to go through all the menus again. However it retained the saved navigation addresses and all seems well with the upgrade. The Sat-Nav is now updated to the 2013/4 version
This is quite an early Sat-Nav which works extremely well. However I did find that there could be a delay in some of the voice commands (like telling me to turn right a second or so AFTER I had turned right) - this "problem" was cured by turning off the RDS function, so I can only assume the delay was due to processor overload.
Note that the RT3 screen is entirely driven by the radio-unit so if the radio-unit is faulty, the screen will not work. The RD3 multifunction screen is a separate unit that monitors the can/van bus for useful info and displays that (so is easily changed if necessary).
RT3 VANBUS: Left-bottom button has 'RDS' on it
RT3 CANBUS: Left-bottom button has 'List' on it.
This would have cost £400 back in 2006
It would be difficult to update a "standard" car as there appears to be significant extra wiring with the JBL system - the amplifier is behind a panel in the boot; and the woofer is in the right-hand under-floor compartment so will have special wiring looms.
Best bet would be to take the system off a scrap car and transfer everything across, but it won't be a simple job.
This would have cost £230 back in 2006
The CD-changer is "96469053XT-New Genuine Citroen / Peugeot 5-Disc CD Changer Blaupunkt - 656476" and until 2015 a few were still available new on ebay. They do suffer from an inability to change CD's as they age so look for a new one as being more reliable.