Dear Rajesh,
SAP MDG is combination of technoligies like Webdynpro,FPM,BRF+,worflow and ABAP OOPS,you got to have exposure to all of this areas but MDM experties in not needed.
As you mention you are good at ABAP,Webdynpro and FPM will be advantage to you and learn the tool easily.
But again I belive zeel of learning will make every thing easier no matter which ever area you belong.
"Where there is a will,there is a way"