My story is similar to yours. I studied piano for a little over four years and then stopped playing for almost 35 years.
When I decided to go back to playing, I knew I needed and wanted a teacher. I did a lot of investigating and actually e-mailed a very well regarded professor who took me on as a private student. I take lessons every other week because it is almost an hour and a half drive from where I live and also because I have to leave work two hours early for my lesson.
I have only had six lessons so far but I know I made the right decision. There are a lot of things a teacher can offer, the very least of which are enthusiasm and encouragement.
Also with a teacher comes discipline. I made my teacher a commitment to practice a minimum of two hours every day. And even with a full time job, part-time consulting work and all the other responsibilities we have as adults (cleaning house, laundry, taking the cat to the vet, visiting an elderly parent) I have kept that promise. In fact I have set up my schedule to get in about 3 hours every day and more on weekends.
Would I have done that without a regular lesson where I have to have things prepared? Probably not.