I have recently replaced the HDD in my daughter’s Mac mini late 2012 by an SSD drive. I opted for the Crucial BX200 480GB.
The installation procedure as detailed by iFixit, is rather easy. Much easier than the iMac 27″. It took me no more than 30 minutes to dismount, install the SSD and close the Mac.
Before that I cloned the main hard disk using SuperDuper! It took several hours for approximately 300GB.
I then configured TRIM on the new SSD using Trimenabler tool.
And the magic happened again. The Mac mini now starts up in less than 20sec . Opening Word or Excel, 1 sec! The difference is really spectacular.
If you are able to do it, I recommend it. If you never hacked into any computer, don’t start though with the Mac.