Classes are great -- but not the Petsmart kinda class, like with someone who is really good (Petsmart in MY area hires basically twinkies with a couple online dog training classes -- perhaps other places have quality trainers???). I found myself a private school with a variety of classes and levels in an indoors clean facility.
A trainer will take you through things that build on things, watch you and give feedback to make sure you are effectively communicating, and the dog is socialized with people and other dogs. If you are worried, ask to meet a trainer or observe a class to see if you are comfortable with their style.
Basic class is may seem a waste because it is not all that hard to go for sit, down, heel, come, stay, but when you lay the foundations and move into an intermediate class, you have FUN and learn so much. You can try other classes too like agility or scent and more.
I recommend a trainer -- however, there is nothing wrong with working on things at home before enrolling.
