How much ATF needed vor 97 V6?

Haynes mentioned 5 qts for both the tranny and the differential. (Your A540 may use the same fill tube, but verify for sure).

3 repeated drains and refills separated by a few hundred miles of driving can be considered sufficient. It's also best to drop the pan and change out the strainer. Don't try to clean the old one, fluid takes the path of least resistance and you can't effectively clean a strainer in a casing. Fram ATF kits for about $20 with a cork-rubber gasket work well for me. And I fill up with Valvoline GM-Dexron III.

Never get a power flush before cleaning the pan and changing the strainer. Some shavings and clutch material just get flushed into the valve bodies and converter. I personally don't believe in power flushes.