Massive galaxies like the Milky Way and Andromeda (M31) form in part from the accretion of less massive galaxies. The chemical and dynamical properties of disrupted galaxies, in the form of streams and shells in the stellar halo, provide a record of this hierarchical assembly process. M31 is particularly crucial for modern near-field cosmology. Owing to its proximity, its stellar halo can be resolved into individual stars like the MW, yet simultaneously be observed from a global perspective like external galaxies. Moreover, achieving a complete understanding of M31's active merger history has broader significance for galaxy evolution, where its disk may have survived a major merger within the last few billion years. In this talk, I will present results from spectroscopic surveys of resolved stellar populations in M31's giant stream, shells, and phase-mixed stellar halo using the DEIMOS instrument on Keck. I will discuss the implications of chemodynamical analyses of these structures for M31's formation history, focusing on the question of a recent merger scenario. Lastly, I will address how M31 will connect the Local Group to the Local Volume in the era of the Roman Space Telescope and ELTs.