We demonstrate a highly-integrated, subwavelength, and reconfigurable nanoscale spatial light modulator capable of modulating the amplitude, phase, and polarization of impinging light both spatially and spectrally. These properties are enabled by integration of plasmonic metasurfaces with phase-change materials. Owing to the ultrafast switching speed, considerable scalability, high switching robustness, good thermal stability, adaptability with complementary metal oxide semiconductor (CMOS) technology, and large refractive index change contrast between its amorphous and crystalline phases, germanium antimony telluride (GST), a well-known PCM, is used for these miniaturized dynamic metadevices. To show the unprecedented capability of this hybrid plasmonic-PCM material platform for practical applications, we investigate a plasmonic-GST gradient metasurface comprising of a patterned array of gold nanostrips that is separated from an underlying reflecting gold plate by a thin layer of GST. While the plasmonic inclusions support enhanced short-range surface plasmons, which are highly coupled to both the electric and magnetic components of the incident optical field, the real-time structural transition between the states of GST constituent, upon excitation with an external electric stimulus, provides a remarkable refractive index contrast for reconfiguration. Such dynamic metasurfaces could lead to new avenues for realization of reconfigurable, fast, and energy-efficient miniaturized photonic components such as multifocus lenses, all-optical switches, vortex beam generator, and grayscale holograms in a reversible and nonvolatile fashion.