Airport Card dying?

Hey all!

I'm hoping you guys can provide me with a little insight / knowledge. I have a 2008 black MacBook with Version 10.6.8. Recently I've been having issues with Airport failing on me. My first warning sign usually comes from my browser pages (I use Google Chrome) claiming to be loading forever, even though the top of my screen says that I'm fully connected to the internet (and my iPhone 4 connects using wifi without a problem). When I go to turn Airport off and then turn it back on, Airport refuses to turn back on. Network diagnostics tell me that Airport and ISP readings have "failed" while Network Settings and Airport Settings are green and fully functional.

Restarting the computer usually gets me to the same spot in about ten minutes. Resetting the PRAM by holding Command+Option+P+R during restart usually solves the problem for a while longer but I find that the next time I use the computer, the problem comes right back. Again, I know the network is fine because my iPhone doesn't seem to have a problem. Is my Airport card failing? Any ideas on what I should do? I'm just afraid of being charged an arm and a leg if I take the computer to Apple and I've heard they're going to stop servicing these computers in August. Is an Airport card something that I can replace on my own?

I'm told that I don't have access to an Ethernet port. I strongly doubt that it has to do with the network instead of my Mac because whenever I seem to have these problems, my iPhone connects just fine and my family member's computers are accessing the internet normally. If it was a problem with the network, why won't the computer even let me turn Airport on to see other networks in the area like normal?

One more update for right now - I was misinformed and DO have access to ethernet - the connection works just fine. The problem is only with Airport.

Thanks - I'll give the Apple Hardware tests a run and see what happens. I'll keep you guys informed.

My hardware test came back with no problems. I now cannot turn airport on even after resetting the PRAM. Help?