I took lessons as a child and teen but didn't get very far.
I want to avoid bad habits and feel that I must, in the words of Yoda, unlearn what I have learned.
If you want to avoid bad technical habits as a student pianist, there is only one solution - get a good teacher.
I've never yet met a pianist who was entirely self-taught who didn't have bad habits. For most of them, that didn't hinder them because they only played simple pop & jazz stuff like melody RH and chords LH. So, why fix what isn't broken for them?
In your case, you've had lessons as a child, so it all depends on how far you progressed with them. My experience is that those who've had several years of decent lessons (and done decent practicing) have a good enough grounding of technical skills which they never forget in adulthood, and can pick up again with no trouble, and then continue where they left off, even without a teacher - as long as they don't overreach and cause themselves injuries or tension problems.
As for music theory etc, you don't need a teacher for them - develop your aural skills and learn from books and YT videos. I've written at length before about how you can practice ear training simply from listening to music (any music) assuming that you already know the basics.