I have two broken engine / transmission mounts. How do I go about changing them?

It is fairly easy to do if you have a lift, but it is possible to do on the ground with a jack and jack stands. You will need to be able to unbolt both sides of the mount and support the engine with the jack while you replace the mounts. If you download the autozone app to a smart pone or tablet it will give you a repair estimate calculator,

When is the last time you had the fluid changed? If by jump you mean it seems to shift late or hard you could have a problem with the solenoid packs. Does the computer throw any codes?

There are many causes for this symptom.
Main suspects include:
worn out transmission
old fluid needs changed
valve body is dirty or clogged transmission filter
worn transmission or engine mounts
wrong transmission fluid added at top-up
shift solenoid broken

This sounds like transmission mounting problem. Inspect all mountings (engine and transmission) and replace broken or weak ones.

Have the van put on a car lift and see if any part is "grounding out on the frame or body of the car, this can be bent exhaust parts or broken engine and transmission mounts or broken vibrations insulation pads on the sub frame.

Vibration at idle brings to mind a few suspects:

transmission mount(s) broken/missing
transmission internally worn
motor mount(s) broken/missing

(1) transmission internally worn or transmission mount broken/missing - test this by shifting into neutral at the next stop light. If the vibration disappears when you disengage the transmission, then the transmission is the source of the vibration. You'll have to inspect the transmission mounts - if they're ok, then the transmission is internally worn and can no longer smoothly "slip" while idling in drive.
(2) motor mount broken/missing - also test this by shifting into neutral at the next stop light. If the vibration persists, then the transmission is exonerated, and the vibration is coming from (under) the engine. The rubber part of motor mounts commonly crack/break and or pop out and are lost.

A photo of the front motor mount for the 2003 Dodge Neon:

BK 6021731 (NAPA) Engine mount Right
BK 6201578 (NAPA) Transmission mount Left Front
BK 6021712 (NAPA) Transmission mount Left Rear

transmission mount broken. have replace. cheap part. not too hard to change.

hello.

so from what i understand, you say when you move the selector from park to reverse or park to drive the car feels as though it lunges, or you can feel the car move into a loaded position forcefully, while watching the engine and transmission shift.

if that is correct, than you could have an engine performance issue, an internal transmission malfunction or simply failed engine and/or transmission mounts,

NOT an issue with your rack and pinion.