im not sure if those engine flushes are a good idea, what if you have some carbon on the rings and you end up cleaning it off?
you might end up with lower compression and even smoke.. unlikely but i wouldnt risk it. Regular changes would be good enough to clean the motor, afterall theres alot of detergents in the oil itself.
nothing wrong with dropping the auto fluid, take the pan off and buy a filter and new oil and put it in,
I think changing the transmission oil every 80K would be a good thing, make sure you get the right fluid and capacity
id avoid mechanics working on your car if you can too, what will most likely happen is that some young punk apprentice will get given the keys and he feel the need to give it lots of revs, do the job quick , then out the door for a full boost cold thrashing round the block, haha, then give you a nice bill and oh your keys!!