Is it a bad thing that I have been playing guitar for 10 years and know virtually nothing about music theory? Would it be harder for me to learn it at this point?
It’s not a bad thing, imho. James Taylor said famously “I don’t read music, I don’t write music. I just wander around on the guitar until something presents itself”. You’re probably pretty creative and have a decent ear. You can hear how some things fit together better than others and you’re willing to experiment until you get something that sounds nice.
That said, if you learn a little theory and can attach it to what you already know, you’ll move lightyears ahead! I mean it. Find a teacher or a book or an online system. Whatever works for you can help fill in some of the gaps in your music head. You’re asking if that will be hard; it will be easier if you can start making connections right away to what you already know. Take small bites at first. And if it’s any help at all, know that we (guitar players) are all on the same path. Best luck to you, my friend!