How hard is it to switch them out? My PS3 fan isn't appreciably noisy (in fact, it is practically silent), but I have to say that you've piqued my interest, depending on how involved the process is.
It's not hard at all. It was very easy to take the PS3 apart. I went really slow, and it only took 40 minutes. The most problem I had was the wrong screwdrivers for the job. Mine were too fat to fit in a few tiny places. I bought a whole new set of screwdrivers for that.
Then, I didn't have a decent precision screwdriver set for the very last screws size #00-#0 Phillips and bought a new screwdriver set for that, as well. (When you get old, you'll use any opportunity to buy new tools).
My 80GB fan goes to the highest speed occasionally, seemingly randomely. It could be doing anything from just sitting there, to downloading, gaming, watching a movie, folding, whatever. I used to have it sitting horizontal, but now I've got it upright figuring the heat would go out the top...but the fan blows out the back. WTF were they thinking with that one? Heat rises, Sony. Besides the noise at certain times it's not that bad. Makes me wonder though.
That's what mine started doing back in August. For the past few months, it stopped doing that, for some reason. I thought it was the much cooler house temperatures. I just hope I don't have a bad heat sensor or fan control sensor, or something. If I do, I'm screwed. I'm not aware if there's a fix for that, or if anybody knows that's even a problem.
I'm reading as much as I can on PS3 YLOD fixes. I have to say, about 15%-20% of the time, they don't work. Worse, if they do work, about 40% of the time it only works for a couple of hours, days or weeks. Then the YLOD returns. That's not good odds, if you ask me.
From what I've read, having the PS3 vertical just might be a bad idea. The air for the fan both intakes and exhausts from all sides of the PS3 that has the vents. Sony did that to prevent it from overheating if one side was being blocked. Makes sense. But, like you said, what doesn't make sense is putting the exhaust below the intakes when the PS3 is standing up vertical. Hot air exits and goes right back in the intakes slots. Very stupid design.