96, 3.8L, 5 speed, base model, stock...

I'll be replacing my transmission during spring break, and I had a few questions. First, I read up that hydraulic mounts are superior to solid. Is that correct? If I get a hydraulic mount for the tranny, do I also need a hydraulic engine mount, or would solid engine mount be compatible with hydraulic tranny mount?

Also, since I'm getting a used tranny from the junkyard, should I change the seals before installing it? I think there's one seal at the front, and one at the back.

Is there anything I'm missing or need to know about changing transmissions before I get started with this project? Does anybody know of places that buy old transmissions that need to be rebuilt?