who can give me the physical for the USDOT Medical Examiners Certificate?
The physical can be performed by a medical examiner listed on the Federal Motor Carrier Safety Administration's National Registry .
what else should I know if I get NA or NI as my driving type?
You will need to send a photocopy of your USDOT Medical Examiner's Certificate  to the Medical Certification Unit, prior to the expiration date of the USDOT Medical Examiners Certificate on file with DMV.