5 - 10 Minuten
The old fan had become noisy - bearings worn out probably. (After taking it out, I could see the blades spun crooked.)
Pretty easy repair, only 3 internal screws. The connector is a little tricky since it's so small, you tend to think you're gonna break it. Go slowly around the edges and it'll come out.
I'll second something someone else said about the new fan seeming much higher quality - spins much easier, though it seems to be exactly the same part. Could be just that the old one was, in fact, screwed up, and it once spun the way the new one does.