I would not go to one of the ones that advertises on TV. They charge large upfront fees and deliver little or nothing in return. One woman (Roni Deutsch  in California) faced numerous allegations/suits and can no longer practice law.

I would seek out a local CPA or law firm that specializes in this area.

In order get an OIC accepted, there must be doubt as to liability or inability to pay. Never seen the first, and inability to pay is rare in the eyes of IRS.