Not that I use a Mac all that often, but based on the »www.apple.com/airportexpress/
site it should be compatible. According to the apple site it can be used as either a WiFi extender or a wireless router by itself. If you are going to use it as the wireless router I would suggest turning off the wireless in the dsl modem. I checked the Frontier help site and found two for their wireless capable modems. It should be simple enough to just follow the steps to get to the area where the wireless can be disabled.
Westell 7500/7550 »www.frontierhelp.com/faq.cfm?qstid=1127
Speedstream 6520 / SE567 »www.frontierhelp.com/usertools.c···atid=191