It does indeed sound like lessons would be a good move. But first & foremost I'd try to ensure you've ruled out/treated any potential pain issues, as this is also a huge cause of this type of behaviour. Saddle fit, back probs, mouth/teeth/bit issues, foot pain... are among some of the potential causes.
Next, while this might sound pedantic(I often do
), it might be about your attitude of 'working' with your horse & you should instead strive to *play* with her. It may just be a mindset issue, or you may benefit from quitting doing whatever you're 'working' on for now & do different stuff, such as tricks & ground games. Or it may be about using a different approach, using a lot more positive reinforcement(Good Stuff), not just negative(removal of pressure).
What to look for in a trainer/instructor..... I would first ask anyone who's opinion you respect for references. Then I'd go watch them work with other horses/riders. Then I'd ask them lots of questions to get a feel for their attitude & approach. Eg. I'd be looking for someone who has a lot of respect and consideration for the horse, not just a bossy 'do this, do that! Make him behave!' type. Not just someone who attempts to force you & the horse into stuff you're not ready or comfortable doing.