They're pretty easy. For the motor you remove the big nuts (lol) holding the mounts to the k member and then jack the engine up a little with a block of wood on the oil pan. Then you just unbolt the old motor mounts, install new ones, drop it back down and torque the nuts.
For the trans mount you just unbolt it from the crossmember, jack the trans up enough to get it out and swap it with the new one.
2000 Mustang GT Steeda #0048
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.