Substituting Airport Extreme for Airport Card on Mac Pro

I have been having problems with wireless internet reception for months on my Mac Pro (5 uears old. Intel). My MacBook Pro works fine in the same space so I am figuring the signal is sufficient. I constantly watch the red lights flicker on (Network Diagnostics) and occasionally I get a "network changed" message. Drives me nuts.

I have an older Airport Extreme and I am wondering if I can use that as a external wireless modem and bypass the internal airport card. As seen in Hardware, card is "working" but if that's the case I need an alternative.

THANKS!