Apple Airport is just like any other router just a slightly different system to configure. Anyways, you can have multiple devices using port 80 since they all bind a local IP. The problem is being able to access multiple internal devices from the same port on your outside IP. If that is not your objective you do not need to worry about different ports. If it is you can change the port based on the startup command:
python ospi.py 8081Or you can setup port triggering to forward ports hitting your WAN to a different port on the inside device.
For the Airport setting up a static DHCP is typically pretty easy and reliable. This is what I have done. It is based on the MAC address.
There is no problem using switches versus a direct connection to the router.
If you have the Wifi hardware in place I am sure you just need to get your Pi connected via software. This guide might help but I have never used it: http://learn.adafruit.com/adafruits-raspberry-pi-lesson-3-network-setup/setting-up-wifi-with-occidentalis
Hope this helps!