I'd go with an instructor. Being a beginner, it's easy to just start again from scratch and learn textbook form. Improvement will be fairly swift after a short while. Instructors will have the patience and knowledge to improve even people with hopeless flaws in their games. A pro player may not. From time to time, beginners ask me to help me with their games. I always oblige, and never accept pay(not a pro btw), but sometimes they have so many quirks and flaws that I don't even know where to start. In those cases I usually recommend an instructor I know, because it is simply too much work and too complicated for someone like me. I can fine tune someones stance if they somewhat resemble a pool player, but if everything is off, its way more difficult. A man's got to know his limitations.
When you become advanced, everything changes. You now need an instructor that plays or at least has played at a higher level and understand the subtleties of the game. Fundamentals is the important foundation of your pool playing house, but you need a roof, too. When you start stringing racks, you'll realize that there is more to pool than just fundamentals. However, without good fundamentals, making progress will be very slow.
I know people who've been playing decades with crippling flaws in their games. They have the knowledge of good players but are stuck at a low level because of chickenwings, jerking their strokes, faulty alignment etc.. Some of them have at one time or another ran many racks in a row, won some tournaments etc. when everything clicked, but they couldn't maintain it, because their fundamentals and psrs are too inconsistent. They spend their pool playing life chasing a dragon that they can never quite catch, forever telling stories of the time they were on the hill against this or that elite player.
Some people can overcome that because they are so talented, but for most people flaws like that will be walls barricading the road to progress.
I didn't take lessons before much later in my development, the first few years nobody showed me a damned thing. If I had a chance, I'd go back in time and get lessons right from the get-go. Instead I had to piece everything together over the course of about 2 decades and with too few lessons in the beginning, more in the last 10 years. I've taken lessons from players and coaches. I benefited from all of them.