Upgrading your Mac Mini with a SSD is definitely worth it, especially if it is going to be your daily driver and you plan to run VMs on it.
I work in IT and am ACMT certified and the guide you are following is pretty much spot-on with the GSX article for replacing/upgrading your drive.
You are perfectly sane for wanting to do this and it really isn't too daunting of a task. Below are some tips from my experiences of replacing these drives:
- Create a Time-Machine backup (As you plan on doing)
- Purchase This Mac Toolkit for replacing the drive and for future use if you plan on taking it apart again.
- Rather than replacing the drive, I suggest keeping it as a 2nd drive and use it for storage. The above drive will include the necessary Parts and Tools in order to do this. Having 2 drives will allow you to ensure all documents are saved/backed up to a 2nd location, in-case Time-Machine failed with your backup. Then, once everything is setup on your SSD, you can turn this drive into either a store drive or a contingent Time-Machine drive.
- Make sure to use the Spudger tool for disconnecting cables. I have seen too many people break cables trying to pry them off with their fingers.
- There are a fair amount of screws/removable parts involved so make sure to pair each part with their assigned screws to avoid losing/mis-installing them.
- Once you have the drive installed properly and everything connected/reassembled, boot into Recovery Mode (cmd + R), connect your Time-Machine drive, and restore from it. This process, depending on how much data you have, should take about an hour or so.
- Once the restore is complete, you should automatically boot into the OS on your new SSD drive and be ready to work. (If you decided to keep your original drive in there and use it as I was explaining in Step 3, after the Time-Machine restore is complete, your Mac may boot into the HDD rather than SDD. To verify, go into System Preferences -> Startup Disk and ensure that your SSD is set to your Default Boot Drive.)
Hopefully this helps and, even though its a bit annoying that you have to gut the entire Mac Mini to replace the drive, its actually a really nice learning experience.
Have fun!!