Realise this thread is old, but thought I'd post my tale of how not to upgrade your unibody 2010 Mac mini here.
Just managed to break the Mac mini two ways performing the upgrade and its in the bin. My other half is furious.
Some background, this was my third Mac mini (both previous were old style white) and I've done numerous DVD drive/hard drive/memory upgrades on them happily over the years.
First problem/mistake; those thermal sensors.
There are three, both I fixit and the YouTube video showed easy (but careful) prising of the connector upward from the housing with a prising tool.
When I did this, the whole tiny housing came off the motherboard rather than the connector inside it. Twice out of three times. The housing is only held on with tiny solder. Be warned.
I'm sure there is a knack to it and goodness knows I zoomed and rewound enough times, but in the end, bye bye 2 sensors.
Second mistake; pulling the motherboard back.
To be fair; one of the two teardowns does say to get a 'mac mini motherboard removal tool'.
I can now only echo this statement.
I put in two small screwdrivers as shown in the other breakdown and pulled gently back.
And broke the motherboard a tiny bit - but that's all it takes.
Turns out, from some post breakage playing, that what you need to use is your thinnest small screwdrivers and you need them both to be feeling like they've made contact with the bottom of the case. It's one of those 'once you know' situations.
Third mistake; the power connector onto the motherboard on the far right.
Just like the thermal sensors, you're meant to prise this up.
This one split in two.
If this all makes me sound like I've used too much force, I'd not be surprised, but frankly the angle and the close proximity to the hard drive make these works trickier than anything in upgrades I've seen for some time.
So there we are.
I'm not saying don't do it, I'm just saying be extra careful and if anyone has any advice about those thermal connectors, post it here!