Hi,
Refer to GNS3 web, there is helpful documentation...
i also starting form zero, now working on VOl I. VPN
you can simulate simple topology with GNS3, routers, switch, and PIX(8.0.4) but from my experiences ... if the topology require IPSec, CA, my laptop starting to slowdown, and some feature does not work, it takes me a lot time to troubleshoot. You also might require ACS for AAA thing and setting up Microsoft CA
But after I tried in virtual Rack, it is fine and working.
So.. it is OK to use GSN3 for simple topology and testing some features..
regards,
bugg