It is very easy to work on FWSM for one who have worked on ASA/PIX. B'coz It also uses the same commands + some additional commands.
you can confiure as many as context in FWSM where each context will act as seperate firewall. So,In a single FWSM you can confiure multipul virtual firewalls.
Here is the link which takes you from intro to advanced config options!!
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