Sat Nav Discs.
 

The dealer I am looking to buy a 2005 GV from says the original sat nav discs could be scratched as the sat nav is not working properly...

Does this sound right or does the GV sat nav system have a common fault?

If it is just the discs can I use any Chrysler sat nav discs or are their specific ones to the 2005 GV?

I have seen someone selling some on Ebay, but hesitant if they don't work...

Ask the dealer if you can have a look at the disc(s). If there are no visible scrateches then I would suspect the dealer is pulling a fast one. Otherwise new discs can be bought from here: LATEST CHRYSLER 2011 SAT NAV MAP CD FOR ALL RB3 NAVIGATION
I bought the full set for my 2007 Voyager. I can recommend them.

Cheers Alan :D

Will one set do all models? I have seen a set somewhere else for sale that are Genuine Chrysler/Dodge/Jeep ones but would they work?

Some of the SatNav discs currently available are for the later units fitted to 2008 + model Voyagers and Jeeps.
The SatNav unit fitted in the Voyager that you're interested in is likely to be an RB3 model, (you can check as the model number is printed on the bottom left of the fascia). You probably only need CD1 which covers Great Britain and is only £19.99 available from the link I posted above. But check the disc that the dealer claims to be scratched first or do what I did and get the dealer to pay for the full set of discs :O)