Yes, I suspect it's on its last legs. I've been moaning about it
here.
To sum up, it started squeaking which led me to run some diagnostic tests and check out the system temperature/RPM of the fan. I lubricated it to stop the mouse impressions and installed Fan Control to keep the Mini cool because I found that the default setup wasn't up to the task - Apple have opted for quiet operation over longevity (the fan wasn't responding to temperature fluctuations at all!).
The upshot of all this is safer temperatures, but more noise.
I've found somewhere online where you can buy the replacement part, but I'd resent paying £25 + VAT + P&P for something that is worth less than a quarter of that. I've bought high quality, super-quiet Papst fans for PCs in the past for under a tenner!
Plus, if these stock Mini fans aren't particularly reliable or quiet I'd rather try something else, though as JG271 and Schtumple say, finding something suitable isn't easy.
This putty knife nonsense still bugs me, but I'm not too concerned about opening the Mini as I've done that three times before and it gets easier after the first time since the catches don't fit so snugly anymore.