Guide worked great for me replacing an old 500 gb HDD with a 500 GB EVO 860 SSD. Just take your time and look at all the pictures and comments in the different steps. They can be very helpful in the couple of slightly tricky areas.
If you do not have any tools, the only unique things you really need are a T6 Screwdriver and a T8 for the Hard Drive Enclosure. Having something like a butter knife to pry with is helpful and having something with a very small tip (preferably plastic but just not a knife) is probably needed to get some of the connectors off easily. The logic board removal can be accomplished several ways. I used a coat hanger to make myself a tool like they showed, but any two small objects can be substituted for the removal tool. Everything else is about keeping calm and being careful. Good luck!
I left mine out as well. Like you, I just can’t see how it is necessary unless perhaps you take your mini on the go and it could be moved around a lot. If the mini is just going to sit on a desk, i don’t see any way that the plug comes out of place.
I used an old coat hanger. I just cut the end off with some pliers and then bent it into a similar shape as the tool. The biggest thing is making sure both sides are about the same length. Also, don’t put your thumbs on the black plastic part on the back of the mini because you won’t be able to pull the logic board out that way.
My drive (Evo 860) was also not initialized. I started in recovery mode and went to disc utility and from there selected the drive. I then was able to use the “erase” function on the drive. I just left the settings as default and as soon as it erased then the drive was ready to go.