Transmission fluid is easy as well. It’s just a lot of screws and making sure the new seal seats properly. They come all twisted up in the box, so it’s best to lay it flat under a book or something heavy and let it flatten out.

There’s no drain screw on the transmission pan, so you have to loosen all the screws evenly (or loosen them all and remove all but 4 opposite each other) and gently take it down while keeping it level. The filter is accessible once you remove the pan.

I’ll never have them flush the transmission. I know of 6 cases personally where someone had the transmission flushed and it destroyed the tranny within months. I believe it’s because tiny metal shavings get forced in places they shouldn’t.
If you do pay someone it should be a legit mechanic, not some lube shop.