What do I do when transmission fluid mixes with coolant? on 2000 Dodge Caravan

Is it hard to replace the transmission gasket? Do I flush transmission as well as replacing radiator. Will a radiator flush be needed after replacement?

Asked by for the 2000 Dodge Caravan
your trans cooler is leaking inside radiator,replace cooler and flush both systems really good
Where is the trans. cooler, is it hard to replace? I've flushed a radiator on a different vehicle before, how do I flush cooler system?