Check in 'Disk Utility' to see if your existing HDD is in the "Lower" position.
If it is, then the change out on your 2012 mini takes about 10 minutes and is quite easy following any of the many 'How to's' available on the web and Youtube.
A big bonus to mounting the SSD internally is you will avoid the hassle of
USB drives being 'ejected' when your computer sleeps.
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