I was in a similar place to you earlier this year. I played for about a year and a half 10+ years ago, but life, profession, and injuries got in the way. In April this year I decided I wanted to get back into it, and took a lesson. The lesson was not the greatest, and I did not really benefit from it at all (read: my experience, not a knock on lessons).
In July I got fitted for and bought some clubs - I had the intention of waiting until I had a consistent swing, but was tired of renting clubs at the range and I came across a deal I could not pass up. Anyways, I took a few more lessons and started reading a ton on here and practicing some drills. I was going to the range 3-5 times a week and my practice was very intentional and methodical. I saw some progress, but not a ton. The problem for me was I could not see what I was doing and it was hard to go off of feel. Ie, one day you hit it great and the shot "feels" a certain way, but the next time that same feel did not replicate the shot. I signed up for Evolvr a couple of weeks ago, and in only two video replies I have noticed a huge difference. I would highly recommend a swing thread on here and/or Evolvr.
So more specifically to your questions:
Fitting: I am similar (6'2) and always had short clubs. Had a fitting and got Ping G25s yellow dot, plus 1". Honestly, given that I couldn't repeat a good swing I do not think it was the best. I am very pleased with the irons, but I think the lie is off for me. I will probably get them adjusted in the near future. So, if you have clubs that work it could go either way - fitting could help, but I would imagine lessons/swing changes would be a better investment if it is a case of one or the other.
Lessons: Go for it. Just be patient and if you have options find an instructor who is good. Hands on has an aspect that cannot be matched with video responses. That said, video offers a lot that in person lessons without video does not. You can rewatch the video and actually see what is happening.
MySwing/Evolvr : Personally, I do not think you can go wrong with these options. Go get a lesson, but also video your swing and start a thread or sign up for Evolvr. The thing I have learned is I can easily see what I am doing wrong, but I cannot determine which "wrong piece" should be a priority to work on. The Evolvr guys (who will also reply on your myswing thread) will help you prioritize your pieces so you build a solid swing from the ground up as oppose to random (correct, but in the wrong order) pieces. You will not be disappointed.