Welcome. I'm pre-op so can't answer some parts of your question but will offer my thoughts anyway.
You could try another diet, but how has that gone for you before? How many have you tried? Did you manage to keep the weight off for an appreciable amount of time? If you did regain, did you end up heavier than when you'd started?
The reality is, most people can lose weight but struggle to keep it off. This is where the surgery comes in, allowing you to explore maintenance without the gnawing hunger your body gifts to you after any substantial weight loss. A psychologist will help with emotional eating issues but won't be helpful with the physiological side of losing and maintaining weight. That's my view, anyway.
As for changing my mind, nah, once I decided this is what I wanted to do, it's been all go. Can't wait, in fact. As I've gotten older I've been accumulating co-morbidities such as hypertension and it's only a matter of time before I get a laundry list of others such as diabetes, sleep apnoea, arthritis and heart disease. Also, I wanna be able to do a bloody burpee before I die, please God.