Yes, it will show on your record, no you cannot get an expungement in federal proceedings and yes you can get a copy of your federal record by following the instructions on this site: http://www.fbi.gov/about-us/cjis/nics/general-information/cgbrochure.
It will show you were charged and the case was dismissed. Be prepared to explai it to your future employer.
My response to your question is a generic response and should not be construed as controlling to your case. I can not effectively advise about your case without knowing all the facts. Additionally, my response does not create an attorney-client relationship. You can contact my office to schedule an appointment if you would like to have me represent you.