It won't be as easy as the 2012 Mac Mini.
According to the AppleInsider review
"It's a fairly simple procedure, though not as easy as some of the previous minis from 2012 and earlier, necessitating a spudger, and a set of security Torx drivers."
https://iphone.appleinsider.com/articles/18/11/06/mac-mini-2018-review-apples-mightiest-mini-yet
Tom's guide mentions that Torx security screws are different than regular Torx screws.
"Just to make things a little more irritating, a standard Torx driver set is not compatible with these screws, which feature a center pin inside the recessed driver slot of the screw."
https://www.tomsguide.com/us/mac-mini,review-5908.html
You also need to remove the fan the access the RAM. It's probably similar to the 2014 model except the RAM isn't soldered down. I'm still waiting for a teardown to know for sure if it's just a TR5 Torx screwdriver that's needed. You can subscribe and click the notification bell for iFixit or OWC if you like:
https://www.youtube.com/user/iFixitYourself
https://www.youtube.com/user/OWCmacsales/
Most reviews said that upgrading the RAM won't void your warranty to do so, though one reviewer said it would, and another just warned that if you wreck anything during installation, it's on you.
The way I look at it right now is:
* For 16GB, the Apple tax isn't so bad. By the time I order the RAM and Torx screwdrivers and have those shipped, the price isn't so different. And Apple does the installation and tests it, which is worth something.
* The Apple tax escalates for 32GB or more though, so third-party RAM becomes more attractive. If Apple was charging a fixed amount for installation and testing, then it might be fair, but they don't. The thing is, I don't personally think I *need* 32GB, though it would be nice.
* 64GB is really expensive, even from third-parties like OWC.