Decided to create a HTPC, of sorts, using a Mac Mini. Wanted it to be as future proof as possible so added an SSD to the second hard drive slot.
Following the guide, which is very clearly laid out (kudos!), it probably took about an hour. I'm slow and methodical, though. Someone with greater experience with electronics (and a greater level of comfort messing with them) could probably complete the SSD addition in a half-hour or less. If you were doing multiple, figure even less time as you get up to speed.
Fairly easy-going, overall. Great guide helped immensely!
A few things:
When replacing the power pack, ensure that the power cord to the motherboard is arranged to leave clearance to properly place the original platter HD.
Always, always (always!) make sure that if you have messed something, you unplug any ancillary connections that you may have already begun reconnecting before yanking everything out again. Ouch!
If you're also replacing ram, don't be a dummy like me. Ensure they are properly seated; otherwise, you'll boot to a whiny, frightening beep. You will then fear that you have killed your computer until you get your wits back. Fun!
Just do it. You'll appreciate the increased speed and responsiveness of your newly SSD-ed Mac Mini.