I have always played by ear and have never had any problems but then again, I started learning when you had to keep lifting the needle off the record to listen to pieces again and again. I have always had a band to interact with, so again, no problems.
Thing is, I recently started thinking, I need something more, so I started getting guitar lessons. Ive always had a rudimentary ability on guitar, but wanted to learn proper like, so now I am finding a completely new interest in , not just guitar , but bass too, as I now have a decent clue about theory and what notes I am actually playing, due to scales and such, so, I would say if you want to really get into your instrument, by all means take lessons, but not just bass lessons. Guitar lessons from a decent teacher will bring you on on both instruments.
Good luck and I hope you are happy with whatever you choose to do