An updated set of goals and objectives for the Mercury Gamma and Neutron Spectrometer (MGNS) are presented based on the most recent findings of the MESSENGER mission. The updated design of MGNS with the new CeBr₃ crystal for detection of gamma-ray along with its benefits for the detection of ⁴⁰K and K/Th ratio are discussed. MGNS will then be capable of measuring the elemental composition of shallow subsurface in order to empirically evaluate the fittest model on the origin of Mercury, as well as the presence of possible water ice deposits on the permanently shadowed polar craters on the planet. We present the results of the first measurements in space performed during the instrument commissioning phase and during the first Earth flyby which occurred in April 2020.