GO TO THE EXAM!!! In zero states is it a good idea to skip the exam. The only question is how bad it will be if you fail to go. Be honest. If you are saying you aren't healed yet and still need treatment, tell the IME doctor. IMEs are used for a variety of reasons and one is to assess is there is a need for continuing care. The IC isn't going to just keep authorizing treatment without an independent assessment.
You can speak to an attorney, but to be totally honest, at this point, if they haven't denied anything, there isn't anything to discuss with an attorney. An attorney will make it much more complicated for you to get direct information about your claim. The adjuster will no longer be able to speak with you directly about your case. You will have to ask your attorney to call them, then wait for the attorney to call you back with the answers. If you run into problems obtaining treatment sure, an attorney can be that middleman, but it would not be my first choice. If you are not sure you are getting appropriate treatment, you can ask your adjuster for a nurse case manager.