G'Sherri, Welcome to linux.org
You have already achieved a great deal....and all of it in the space of 4 hours.
Becoming conversant etc with Linux is a
mindset thing.
Don't worry about membership upgrades etc etc, they are not required, but if you wish to you can do that at a later date that suits you.
I cannot see that you have spoken of any preference in the linux stable.......so may I suggest you start with the one which has the most support and is arguably the best known
Linux Mint (cinnamon desktop) 20.1 .....(supported until 2025)
You can always look over places like DistroWatch and become perhaps seriously confused, but I will leave that decision to you.
In a nutshell....download the .iso file ....use a program like Balena Etcher (on windows
or on Linux) to 'burn' the .iso file to a usb stick (8gb is good, 4GB will do) and then
boot the pc to that usb stick.
You will need to change the boot order to do that.
(May I suggest you do that on a "spare" pc or laptop?.....just so that it will not tie up a pc that is running autocad and take you away from your work.)
When Linux boots, it will be running in
LIVE mode....that means it will not be running on the Hard Drive....it will be running in ram,
memory.
AS such you can do no harm.
Take it for a run...do whatever you like with it....it will be a touch slower than a full install, but it will give you a good idea.
If you dont like Linux Mint, try Ubuntu (choose a distribution (distro) that is supported for at least a few years before you need to upgrade)
Just a thought....in Linux, after you have it installed etc etc...you can always try running windows 10 in a VM (virtual machine)...especially if you have a lot of RAM).....
That way you avoid the crap of windows, but also have the bonus of continuing with the genuine auto cad.....maybe ??
If you need a helping hand, just yell out. We are here to help.
(Edited many times for typos!)