Reinstalling the OS was the only tricky part. Make sure you know how to do it!

Mon problème

Old Mac mini was severely hampered by an old disk hard drive.

Ma solution

The physical repair is very nerve-racking, but they are very very clear.

Mon conseil

Hold option while rebooting to restore the new harddrive from a time-machine backup. (I couldn't figure this out for an amount of time that was embarrassing.)

Make sure you know how to reinstall your OS!