I bought a HAYDEN tranny cooler at ADVANCED AUTO for $49.99 + tax. Very easy install and worth every penny. I think it took about 1.5 hours to install.
What was your idle before you swapped throttle bodies? I disconnected the battery when I swapped mine and reconnected after the install was complete and it ran great. It sounds like you might have a leak somewhere.
You don't need a gasket for mounting it to your lower intake. There is an o-ring type seal molded into the lower intake. I hope that is the info you was needing.
Yes, do use the new nut. If I remember right from the rod up, it should go in this order:
Bump stop
Steel plate
Rubber bushing
Metal washer
Nut
This is on the struts. :nice: