A preassembled modular drop-in transition having internal components in conformity with assembly and function specifications prior to and after insertion into an industrial gas turbine access port. The transition assembly maintains conformity with those specifications after insertion into the combustor case if it does not inadvertently impact other turbine components during its installation. Inadvertent impact is avoided by having a combustor service zone proximal the combustor case, enabling slidable insertion of each transition and/or combustor assembly into its corresponding access port along its corresponding insertion path without contacting other turbine system components. A multi-axis motion transition handling tool (THT) in the combustor service zone, preferably under automatic control, is coupled to a transition and facilitates precise alignment along the insertion path. Automatic control facilitates consistent repetitive transition installation and removal by executing a sequence of stored pre-determined manipulation steps.