i have a 99 sl2 wanna change the trans fluid and filter. how many quarts does it usually take when changen the fluid and filter?

~4 qts. A 1gallon container from walmart is perfect :)

Or as many as it takes to read full on the dipstick.

Another way is (assuming your current fluid is to the correct level) would be to collect all you take out, measure, and put back in the exact same amount.