I know the feeling, I've been doing Mac/PC support for going on 30 years, and sometimes...
However your gmail address got connected to your AppleID it is not that difficult to change the email address associated with your AppleID. As long as you have another email address that can replace your gmail address.
Me, I have bunches of email addresses and even a whole domain if I want it so that is no big deal for me (I'm an IT geek, what can I say) but in order to do this you need another email address that you currently have access to. Because an email address IS your AppleID, that is the only way it works.
First go to https://appleid.apple.com/ and sign in with your AppleID username and password which will be your gmail address and whatever password you set. (not your Gmail one!).
Once you are signed in, at the top of the page is your Account information and over at the top right there is an "Edit button. Click on it.
At the top of the next page there will be a link that says "Change Apple ID..." click on it.
It will ask for another email address, type that in, click continue and follow the prompts to change it from your Gmail address to the different email address. Sorry I don't have more details after that but I don't want to change my AppleID here ;-)
Once that is done you can sign out and continue to use your Apple devices as before, but with a new Apple ID that you just set.
It has been a long time since I did any of this so you may have to sign out of your Apple ID on your Mac/iPhone/whatever and then back in with your new AppleID email and password. If you need help with that post something in the comments to that effect and what you need to change it on (iPhone/Mac and the OS versions) and we can assist further.