First off I'd like to say hi to everyone! I'm hoping I can find some insite from you guys/gals here. (this isn't what I wanted the first post to be but so be it)

I just signed up for the page on behalf of my girl, she loves her 2007 Mazda 3 GT hatch, but is having some issues with her transmission.

The good ol AT light is on (P0753, Shift solenoid A)) and her engine light is on (P0131/4 02 Sensor low ouput)

O2 sensor stuff I can deal with and have changed many in my lifetime wrenching on cars.

The transmission shift solenoid one, well comes with a couple noticeable problems and I want to know what my first steps should be.
When in park the car starts and runs fine, the AT light is on though unless I reset the code using my OBD2 scanner, but if you shift to reverse or drive, you can feel the transmission quite fiercely go into each mode with a bit of a clunk. We haven't driven the car since the light has come on in case this can be repaired before blowing up the transmission.

Something tells me this isn't just a solenoid.

Any insite/advice is welcomed. There are a few tcm's and transmissions around for sale if it has to come down to it as well.

Thanks for any input!