You have a shifter module (whether it's called ESM or not, I don't know - there is no mechanical linkage to the tranny for the gear positions 4 through 1). It's a box with a transmission range switch in it that sends a signal to the transmission. If the shifter won't move, there's something mechanically wrong in the box.
If you wanted to dive in yourself, I would definitely get a manual or diagram first.
You can definitely replace it yourself by removing the center console, but I imagine it carries a pricetag intended to trigger the "fight or flight" response in most humans.

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