Try
http://www.garmin.com/support/faqs/ . This should answer many, if not all, of your questions. You can also download manuals.
If you buy a 60csx, in short - you will need a full version of City Navigator (CN) which gives you the maps. Mapsource is a piece of software for your computer (PC) which will allow you to plan & download routes to your unit, as well as transfer maps. Mapsource will be included with City Navigator.
Incidentally, a stand-alone version of CN is quite expensive (not sure how much), but it might be more cost-effective to buy a 2610 (currently around £180) - which will come with CN - & use its spare unlock code on a 60csx.