FWIW - was concerned about flushes given my understanding of flushing agents involved. However, it seems some newer flushing techniques are nothing more than running new fluid through until it drains clean. This newer technique seems kinda wasteful, which may account for some of the high price.
At any rate, always been a pan drop and filter change guy. Suggest if your fluid is anything other than a good red, good red meaning more red than brown - consider changing it now.
Had good results with changing once a year - which amounted to about 30,000 miles. The first two changes were concerning - lots of crap in the pan and stuck to the magnet. After than, pretty uneventful, just a light film on the pan and magnet.
Even so, still had the occasional burp where the tranny wanted to start from a stop in something other than first. Just took it easy for a couple of starts and things are good for another couple of months until the next event.
Suggest 7 qts 13 oz is a good target on the pan drop - seems to put things right back on the Full mark. Yep, the gasket is reusable - still using the original. Did change the filter seal after the fourth change, just cause it seemed to be getting a little loose when inserting the new filter. Recommend to not go cheap on the filter. Partial to the WalMart SuperTech Dex6 for price and meeting spec.
Hope this helps.