Some people will say that you should go to an ortho, that they are more experienced, but I just went to my dentist. They have to go through a certain certification training in order to do invisalign so I'm confident they've learned what they need to.
As far as cost, It doesn't matter, the dentist or ortho is going to charge you what they want to. My dentist is a bit pricey and for an 8 month treatment plan it's still gonna cost me $5500, but whatever, I want invisalign so I will pay.
Still eagerly awaiting my aligners!!!