A seventeen year old transmission with say 80,000+ miles and pronounced problems is like a 109 year old human. Protein powder, may be overly optimistic.
After being in the business a limited but extremely education rich time (cutthroat competition) I came to a conclusion that still stands today...
An automaker brand rebuilt transmission is almost impossible to meet never mind surpass in quality and dependable performance.
GM for instance was using all new valve bodies on its THM 400 units, new heat treated clutch drums, reaction shaft, and a larger boss on it's pump casting. No way could I access this stuff aftermarket.
What is today's program? Mr. Goodwrench? The transmissions cannot compete price-wise with scumbag rebuilder craft but then I could not produce a me-too twenty nine dollar lifetime guaranteed alternator. Not and keep my sense of dignity and ethics intact.
GM uses molded plastic shipping boxes to handle their transmissions.
But the transmission cooler(s) and lines must be flushed out.
I would use the largest aftermarket cooler and follow the maker's instructions for mounting.
There used to be a kit called a Transgo-Tow-And-Go valve body modification that seemed to improve the lifespan of heavily loaded automatics but in the age of computer ECU's I sure would check a valve body kit for compatibility and wait until the factory warranty has run out before installing it.
Good luck and if you do your own work, stay safe.