As a followup, I finally serviced the transmission a few weeks ago. I used the Fuchs 3353 (I think...bad memory) fluid. With no torque converter drain plug on the 2001, I instead disconnected the trans cooler fitting at the lower/center of the radiator. The transmission was kind enought to pump out surprisingly close to all the old fluid though the dangling flexible hose. I bougth an extra liter or 2 to permit flushing out the old stuff.

Dropped the pan to change the filter. It was shockingly clean. After 70K with no service, the pan was absolutely spotless. There was no debris whatsoever.

Took it for a drive, and wow! Much improved. Even the gear changes that were fine before are better now. The 3-4 and 4-5 that were the basis of my original complaint are greatly better, but not quite seamless. After a few hundred miles it seems the trans is adapting and things continue to improve.

Highly recommended service.