Get some SeaFoam Trans Tune. Put that in there now, Drive it for a while, say 50-100 miles. This will loosen and dissolve any varnish and other stuff in there. Then drain it, put the pan back on, and refill with the old filter. Drive around for about 10-15 minutes like this, I would say around town is best...get it all mixed up.
Then bring it home and dump again, watch out, its SUPER hot. Now take out the filter, just pull straight down from the neck of it, twisting a little wont hurt, just don't push it any way it doesn't want to go, that would break it off inside and then it kinda gets annoying.
Now install the new filter, clean the pan and magnet out, nice and clean. Then take the new gasket and apply that to the pan. You might need some petroleum jelly to keep it in place as it has probably been curled up in the box. Now torque all bolts gradually, in a criss cross pattern, to about 14 lb-ft. Now reinstall the fluid in the transmission, start the car and you're done! Make sure to check for leaks.
1 Torque Wrench
1 Jar Petrolleum Jelly
1 Ratchet w/Socket
12 qts Dexron transmission fluid (6 per each refill)
1 bottle of SeaFoam TransTune
1 ProKing Transmission Kit (this one is recommended because it comes with a rubber gaskets and not just a cork one)
*edit* sorry about the offtopic don, i was typing this when you were typing yours.