I feel this is SF worthy (as opposed to SU) as I go into a bit of detail on gateways/routing.

Here's my ideal setup (if possible) -- there is a wifi network (lets call it bob's) with which I want access to, but I have a few other computers on my network which I want to keep behind a firewall.

So I was thinking of buying a wireless access point so that I could set it up to connect to bob's network from the AP, and then from my server, connect to the AP via ethernet. So that's the first bit. Second part is that I want to have my own private wifi network off the back of this; can I then tell the AP to serve a new network called foobar.

When I say private network, I mean that my server is actually a Debian linux install with routing configured (and I also do some QoS stuff on, etc). So ideally, I'd like all the clients on the private network to be behind the server in terms of routing. However, if the private clients connect to the server via wifi, then aren't they exposed to the "public" network? That is, if someone is savvy enough to scan for my IP range.

Also, to do routing I'd need to connect two ethernet cables between the server and the AP (because you can't do routing/QoS on virtual devices) -- which isn't a problem really; but I'm not sure whether the AP will allow me to separate the public and private LANs.

Or, as well as the AP, am I better getting a wifi-to-ethernet adapter for the server? I could use a wifi usb, but this can be tricky to set up on headless linux; plus the signal strength is a bit lousy.

If this question is a bit vague/spurious in places, please comment and I will explain in more detail.