Yes to both questions. An USB hub will work just fine, I have 4 USB devices connected on my WL500G.
To allow windows filesharing you will need to configure SAMBA. Search this forum for loads of usefull information on this topic. For filetransfer I would like to suggest to use SCP (with the windows client WINSCP) and not use the insecure protocol FTP
You will also find some information on wl500g.dyndns.org. You may want to use Oleg's firmware anyway, that's the place to find it!
Have fun with your new WL500G
Peter