Anyone know how to remove the big fan from a Antec 900 case?

I have had my gaming rig for well over a year now and I have never taken the big fan at the top out to be cleaned. I have used compressed air and did my best to clean it off with a q-tip.

Anyone know how to take that big fan out of teh case for a thorough cleaning?

Also, can someone give me an idea just how long thermal paste like arctic silver and ceramique last? I had replaced the thermal paste on my motherboard (EVGA 680i SLI A1 Revision) back when I first got it before I ever booted the new computer up (I built the computer myself). So I'm not sure if there is a life span of how long the stuff lasts or not. Since I am in the process of completely cleaning out my computer, I may as well take the time and replace stuff that needs replacing.

I guess I do have one other question. I had bought a BFG 9800 GTX+ Video card about 6 months back and I never touched it's thermal paste. I was wondering if BFG was like EVGA and allowed you to remove the heatsink and apply your own thermal paste without voiding your warranty. If you are unable to do that, it's not a huge deal, but would be nice to know either way.

Thanks in advance!