A fluid end assembly of a reciprocating pump has multiple fluid end bodies that are removably attached, independently of each other, to a power end assembly of the reciprocating pump, and to a manifold of the fluid end assembly. Each fluid end body defines a discharge outlet that is coaxial with a plunger bore for a reciprocating plunger, and a suction inlet that is disposed above the discharge outlet. A valve assembly is removably insertable into a valve port extending from an external surface of a manifold attached to the fluid end body, without having to remove the manifold from the fluid end body. The valve assembly includes a valve mechanism surrounded by a cylindrical valve body that lines the internal wall of the manifold defining the valve port, thereby forming a barrier between fluid flowing through the valve assembly and the internal wall.