Adding gauges to PMDG aircraft

I would like to install a Map and GPS gauge in the PMDG 747-400X for FSX but am having a difficult time doing so. I realize PMDG has made it very difficult but I wonder if anyone has any luck in adding any gauges to this aircraft. I have FSPS but it cannot help me in the editing. I have a valid purchase of this aircraft from PMDG.