[Cialug] [OT] Private LAN connected to building WLAN for Internet Connectivity

[Claus]

I'm the technical guru for a non-profit organization that is considering 
to switch from its dedicated DSL to a building wide shared network.  The 
idea is that we'd be saving about $30 a month.

Currently we have a wired network and a wireless WPA network which is 
used by 4 desktop computers, one laptop and a samba file server. 
Internet connectivity is provides a 1.5 mbps Qwest line through an 
Actiontech modem.

Under the proposed model the Internet connectivity would be provided by 
a 7 mbps Quest line that's shared wireless throughout the building with 
all tenants and visitors.  The building's wireless network will be open 
to all.  The wireless routers are rented from Qwest and are supposed to 
be "industrial".  (BTW, I'm not responsible for the building wireless 
network.)

I imagine that we still would need to keep our private LAN in order to 
use the samba/windows shares without having to worry that everybody can 
access our data.  Since we also have a laptop that will need to access 
the samba shares we need our own protected WLAN as we currently do.
So I was thinking about setting one wireless router up as a bridge to 
the buildings wireless internet, providing us internet access, NAT, 
DHCP, and hopefully some control on what ports are open/cosed (aka poor 
man firewall/packet filter).  Another wireless router or access point 
would be set up for our WLAN.

My questions:
- Which router would be recommended to run as a wireless client and
   provide Internet connectivity, NAT and DHCP for our local LAN?
- What pitfalls might I encounter?
- Is is a bad idea to rely on an open wireless network for Internet
   access?

Setting up Internet connectivity through a wireless network for a wired 
LAN is something new to me.  So I'm very grateful for your help and 
input.  Thanks,
   Claus