Two, count 'em, Two repairs thanks to iFixit!
Il Mio Problema
I replaced the internal SSD with one from OWC and my fan started running at high speed - LOUD. It turns out that something caused the fan blades to start scraping against the housing and my fan either didn't run because it was stuck, or it ran at full speed screeching.
And at the same time, I was getting frustrated because my mom's 2012 Mac Mini ran like molasses in January due to the 5400 RPM HD and not enough memory so I swapped an SSD into the lower drive bay. And iFixit helped with that too!
La Mia Riparazione
Since replacing the fan requires removal of the CPU heatsink, I also ordered Arctic Silver ArctiClean and Arctic Silver Thermal Paste. The ArctiClean kit has 2 bottles; one bottle of remover to dissolve and remove the old paste and a bottle of prep to make the CPU and heatsink "stickier" for the new paste. The instructions were perfect and it took me about 45 minutes from case open to case closed to replace the fan. Now the fan runs quietly at all speeds and spends much of its time between 1,000-2,000 RPM, which apparently it couldn't do before because of the friction.
Il Mio Consiglio
Take your time; it's not a race. I use a Donegan OptiVISOR and a keychain flashlight and check out where everything fits before I start taking things out. One of the stranger parts is the rubber gasket that goes around the heatsink and it has little tabs which fit around and in-between the fins. If you don't put it back in correctly it will make noise.
Don't skip removing and re-applying the thermal paste -- that will lead to tears later on. Yeah, the parts are expensive and you may never use them again, but it's cheaper than a new motherboard.