I'm right there with you Brother. I have and LOVE my 8300. I brought a P9750 (latest & greatest and all) but that 8300 has just been Rock Solid. It amazes me still, how long it can sit and just be ready to go, when it's time to Print.
If that message is there BUT THE SECTION is FINE. I'd let him replace that fan. And if that doesn't fix it. I'd just keep printing. I would not want to fix it bad enough to go mucking around with main boards and all that. For all you know that could introduce its' own Problems.
(That's if the Section is actually functioning [but the Printer is just throwing the message])
I'd put in some light paper and turn the Section to high and if you notice, be it visually or audibly that that Suction is excessive, as it should be with a High setting and light paper, then I wouldn't worry about it.