This site is a good site.
You can download and burn to a disc the firmware updates and gracenote updates from this site for free. You will need to know what version of software you have. On this site you can look at the history of when the updates came out, and what isuues this update fixed and what new features were added.
On the Gracenotes it works the same way.
I used this site and burned the newest versions of firmware and gracenotes and it worked perfectly for my RER.
NOTE: these are not NAV updates, only firmware and gracenotes. The NAV updates are done thru NAVTEQ and are not cheap.
ALSO if your version is more than 2 versions older than the most current, you may need to install the other updates in the order that they came out. Sometimes trying to add the newest version onto an old version doesnt work out.