 RE: GPS Accuracy
OK, a couple of things. First off don't worry abuot the accuracy of the GPS. The accuracy does not degrade over time as the GPS wears out. Either the thing will work or it will not work and if it does work it is getting the best accuracy possible at any given moment. There is a "Works", and there is a "Doesn't work", but there is no inbetween.
On the charts, and the problem is that the world changes but a particular version of a chart doesn't. The Blue Chart system derives its mapping from data gathered by a firm called Navtronics. Navtronics gets its data from nautical charts that are available to anyone who wants to buy them. What you see in the Blue Chart systems is exactly what you would see if you had bought the underlieing paper chart. So when you are thinking about electronic chart updating first you have to have had the underlieing paper charts corrected (are you familiar with Notices to Mariners?). In general any given paper chart won't be updated any more often than about 3 years, and most of them don't even get that sort of frequent look. Also, your Blue Chart area is made up of quite a few individual paper charts, hundreds of then ususally. So just because a chart has been updated doesn't mean that the area in which you operate has updated information on it. Do you see where I'm going with this? Updates are infrequent and generally not all that much worth putting your money into.
However, if you have to have them I believe that there is a part in the Cartography section of the Garmin site where you can find the version dates of the various charts used in any particular area of coverage for a Blue Chart. I believe they have some sort of exchange program where you can basicaly get some sort of credit for your old chart when exchanging for an updated on.
Thom | 
