Changing The Fans On Ex470 - Possible?

It's time to do some maintenance on my EX470. It's been running since May 2008, and all I have really done with it is to put in some disks and changed the ram.

Anyway, I usually take the time to remove all the dust and stuff from it about twice a year. I don't remove all the panels and stuff, but I do remove all the disks and take the top off. I use compressed air to blow the dust out, and the assemble it again. Upon inspection, I found that the fans were in need of some thorough cleaning. I did my best but it's a really tight squeeze to get my hand down there. When I booted the server, I heard the fans spin up. After running 24/7 for more than two years, needless to say are ready for retirement.

Have any of you changed the stock fans? As far as I could see these are 80x80x25 mm fans with a 4 pin connector. I was thinking of ordering a couple of Papst replacements, but I would like to make sure that these are the correct specs first. Is it even possible to get them loose, I will have a hard time getting my hand to fit down the tight space to maneuver the fan in place.

I would appreciate any feedback!

-T