the way to replace it with the engine still in the car is an urban myth i think lol.. there might be a way but i tried and tried until i just pulled the engine..
unbolt the mounts.. take a jack and a block of wood.. jack the motor up off the crank (balancer).. drop it, stick the other one in.. and drop the motor down
should be able to.. just silicone it to the pan first off.. let it sit with some bolts holding it in place.. when the silicone dries the cork gasket *if thats what your using*.. should hold on just fine.. slide er in there and bolt it up.. im going off of common sense and the thought of me having to do it as well to tap for lines oneday.. i had to replace motor mounts in my car with the prothane's and jacked it up the same way.. and just looking up there gave me the idea of doing it that way.. best off unbolting the mounts and jacking it up first.. good luck
just run to the parts store.. get that and some silicone if you dont have any.. take the pan your using and stick a bead all the way around it.. and drop the gasket on it.. get em in place.. stick a couple bolts through diff holes all the way around and line it up.. let it get good and dry for the most part.. then do the harder part while she dries