I'm still a noob but I will probably advise against dual booting in the future. Trusting the Ubuntu forums for my Linux Mint problems was probably my first mistake. I was dual booting Linux Mint/Windows 7 at the time and I guess I was allergic to documentation for some reason. All the reformatting of Linux Mint somehow corrupted the boot partition of my Windows 7 so I reformatted for Windows 7 and left it that way for nearly a year.
I couldn't understand that maybe I was reading the right answer for me, but I had to modify the information to fit my distro. Or the silly things like oh, I'm tired of Cinnamon I think I'll try Gnome; afterwards I apt-get autoremove.. people on all the forums will say, "Go ahead, there's no way it could cause any harm." So I restart the computer and I'm missing an entire environment and a slew of other important packages because they're somehow linked to everything because everything was automatically installed and is no longer needed.
I did that as well once, ok twice, second time I knew how to fix it. And yes, I had probably read the same threads as you, which lead to it.
)
Here's why it happened, and you are somewhat correct on why, you were reading Ubuntu's help.
Ubuntu uses the Unity desktop, if you put Cinnamon on it, you still have Unity. Remove Cinnamon and you can fall back to Unity.
Mint uses Cinnamon, which is built on top of Gnome, it's a fork of it. So when you tried Gnome, you overwrote parts of Cinnamon but it would still function (somewhat). Then when you removed Cinnamon, it removed HUGE chunks of Gnome. It's possible to do what you wanted, it just needs to be done in a certain order, or you need to repair Gnome (reinstall) after you removed Cinnamon.
The big question though is did you learn from it and did you have backups?
You're going to make mistakes, big ones, this is kind of why I see partitioning as sort of a baptism or test. Windows and Mac users typically buy a computer with an OS already installed and optimized, this time it's you having to do that and it doesn't always go perfect, especially with an open source os, things will go wrong and you need to be able to deal with it. Think of it this way, you already experienced the worst that can happen and you passed. If you didn't kill it then, you probably would have later (and still could again).
Even with the best documentation things happen.
I was experimenting with Arch and put Cinnamon on, all was great, and then I installed Virtualbox. There's a little known conflict between those three, and it causes the entire system to dump. Unless you look it up the right way, you wouldn't know it existed and who would expect it.
Remember, with great freedom comes great risk, this wouldn't happen on Windows, but remember, you can't change the entire desktop on Windows. It's why IOS is so stable, you can't do much to it and muck it up. Open IOS up to the customization Android has and you would see it come crashing down. That's not an insult to Android or IOS, what you prefer is personal.