Transmission mounts are fairly easy to change. Do not attempt to change the mounts unless you have a car jack handy to support/lift the transmission (just a normal jack, im not referring to anything special; scissor jack, hydraulic jack, whatever). The reason you need a car jack and cannot use a jack stand is because 1. You will not be able to lift the transmission and tighten the bracket at the same time and 2. Your old mounts made the transmission sit lower because they sag over time, when you put new transmission mounts in they are taller and not sagging, hence the transmission must be lifted slightly higher then before.
ALWAYS USE JACK STANDS WHILE THE CAR IS LIFTED! Do not trust a car jack to support your car while you are under it!
Step by step process:
1. Remove the top nuts (13mm) from the top of the mounts, in my diagram I have labeled these nuts by the number 1.
2. Support but do not lift the transmission with a jack.
3. Undo The bracket nuts (13mm) on the outsides of the brackets. I have labelled these nuts as number 2. The picture does not illustrate the exhaust that travels right below the passenger bracket nut. You do NOT need to remove or lower the exhaust, I was able to easily undo the nut with a 13mm wrench from the passenger side.
4. Remove the bracket with mounts still attached from the car.
5. Remove two 13mm bolts holding mounts to bracket.
6. Put new mounts on bracket
7. Jack the transmission up to the point where you can tighten the bracket nuts (number 2) without the transmission touching the mounts.
8. Slowly drop the transmission back down onto the mounts
9. Tighten the top mount nuts (labelled number 1 on my picture). Do not overtighten as I have found some cheaper mounts are prone to breaking off the stud.
10. Recheck that all nuts are tight.