A gas turbine engine unit (110) for use in a modular power generation system includes an engine package (112) and a mechanical handling system adapted to convey components (114) out of and into the engine package (112). The engine package (112) includes a floor (132), a plurality of side walls (136), and a ceiling (134) that cooperate to define a sheltered space (140) sized to receive a gas turbine engine. The mechanical handling system includes rails (121) adapted to support components (114) conveyed out of and into the sheltered space (140) defined by the engine package (112).