One time I replaced a sink in this beat up mobile home I had that didn't fit the hole right. Ended up cutting the hole bigger for the new sink. Doable, but only if kitchen drawers and such are not in the way underneath the countertop.
again, also depends what your existing countertops are made of
overmount for tile or formica
undermount for granite or quartz... but if this hasn't been done in the past edges may not be finished/polished