A number of special exhaust tools can be rented or bought from a local auto parts store. A common one is a tail pipe expander, designed to enable you to join pipes of identical diameter.
It may also be quite helpful to use solvents designed to loosen rusted nuts or bolts. Soaking rusted hardware the night before you do the job can speed the work of freeing rusted parts considerably. Remember that these products are often flammable, apply only to parts after they are cool.
The Mitsubishi exhaust system generally consists of four pieces. At the front of the vehicle, the front section of pipe connects the exhaust manifold or turbocharger to the catalytic converter. The front pipe on some models contains a section of flexible, braided pipe which allows the system to move without breaking. The catalytic converter, a sealed, non-serviceable unit, can be unbolted from the system and replaced, if necessary.
The diesel engine does not require a catalyst and no converter is found on diesel powered trucks. The gasoline engines in the truck have two catalytic converters. Although they are referred to as front and rear converters, they are attached to each other and are located immediately below the exhaust manifold. Replacement of the front (upper) catalyst requires removal of the exhaust manifold before removal of the converter.