Hi Cliky - yes a successful weekend thanks for asking and here is where I am at now.
I have been unlocking the radio from the housing pulling it forward and as soon as they are reachable - disconnecting the plugs. This time with more thought I decided to work downwards, so I pulled off the trinket tray and the air ducts which gave me sight of the back of the radio - and I found disconnected the Fibre optic cable, as you had previously suggested, which had come out of the multi plug housing.
Although I have had at all times the blue screen and the Fiat logo displayed, connecting the fibre cable immediately gave me a display much better than I had seen for the brief time I had it working after I bought the car and with all the functionality so far as I can see. I have played with it today and the orange light has stopped pulsing the radio stays tuned and the CD stacker works.
One other possible factor is that the unit has been off the car for so long it was totally flat in that the date and time were all zeroed and I have seen a suggestion that this in itself can unscramble a confused unit
However after testing I still have the original problem in that the integrated CD Drive will not read or play a CD of any type (music or map) and therefore the Navigation function is inoperable.
I then carefully took the RT3 apart and gained access to the CD Drive and the laser lens and cleaned it up and then connected it back up to the car whilst disassembled to see what went on in the drive. The disc is quite happily sucked in and it starts to spin but only slowly and a bit spasmodically not picking up speed as I would expect. Pressing the SOURCE button on the unit only cycles between RADIO and STACKER and not the CD that presumably should be included and perhaps indicates that it is US.
I have all the model numbers for the CD which is a Phillips unit and seemingly is not easy to come by anymore. I have found a couple of possible's on the NET and have sent off an info request and I will let you know what comes of it.
However for the moment I am very happy and grateful for your success which pushed me into having another go. I now have lots of functions (and music) that I have been without for 6 months and if push comes to shove and I can stay with what I have now and use a TomTom but I will try to resolve it if I can find the parts or someone who can repair this unit.
Regarding the Lexia/PP2000 kit, did you manage to get a Win 95 PC that matched his stated minimum spec of memory and processor speed, if not what has yours got in the way of spec and which is presumably running it quite well from what you say?