Airport Extreme Firmware on a mac mini

[lunas_padre]

Hello - About a year ago I purchased a Mac Mini with the following specs:
1.83 GHz Intel Core Duo
2 GB of Ram
Airport Extreme Wireless Card

I connect to the net via wireless connection.
I have noticed as long as I have had this machine the speed of the page rendering on the net varies, regardless of the site.
Sometimes it is pretty quick, and other times I will have to wait a minute or 2.
I do not experience the delay on the computer which I have attached to the net via wired connection, and I am generally going to the same locations on the net.
I was doing some searching online, and one of the reoccurring suggestions is to check, and if necessary, update firmware for the Airport Extreme wireless card.
The problem is when I go into the Airport Admin Utility there are not any Airports listed; therefore I cannot check the firmware version.

The Mac Mini is about 30 feet from the wireless router it connects too.

Could someone tell me how I check the firmware version for the Airport Extreme Wireless Card on a Mac Mini

I run the apple software update once a month, and the current os version is 10.4.11.

Thank you in advance for your response.

Chris