A number of special exhaust system tools can be rented from auto supply houses or local stores that rent special equipment. A common one is a tailpipe expander, designed to enable you to join pipes of identical diameter.
It may also be quite helpful to use solvents designed to loosen rusted bolts or flanges. Soaking rusted parts the night before you do the job can speed the work of freeing rusted parts considerably. Remember that these solvents are often flammable. Apply them only after the parts are cool.
Note that a special flexible coupling may be used to connect the exhaust pipe to the exhaust manifold. If this important coupling should develop a leak, be sure to replace the seal ring with a quality part, install it in the proper direction, and torque the bolts to specifications. Check also for any cracks in the exhaust pipe, exhaust manifold, or flanges and replace such parts as necessary.