That's a valid point, but even people with tons of aptitude can smoke a trans if they don't know exactly how it's supposed to operate.
Hell, I have no clue how I would set a 518 and would probably be here asking a million questions before monkeying with one. Not that I would build an auto car, but that's another topic, haha.
You're 100% right though. Once it's right, op is going to have an even harder time parting with the car..
I'm hoping he strikes gold Monday (he's due!) and gets a trans tech who is worth 2 ***** and helps get the kickdown AND throttle squared away because a good one should be able to without question.