I have done mine 3 times in 100,000 miles. The first change showed a lot of metal powder stuck to the inside magnet so cleaned that off and changed the filter then did what Jon Joey described to get the fluid out of the torque converter. I used white tissue with clean trans fluid to compare with the old trans fluid. When the fluid coming out of the line looked the same as my sample I stopped. On the second change there was less metal fillings stuck to the magnet,the third change was even less. The lessen I learned was reuse the original OEM gasket rather than the new gasket that comes in the kit. I used the new gasket and the pan leaked even when I re torqued pan bolts. I ended up putting the old one back on, it had steel bushing around each hole preventing pan distortion the new gasket was just rubber.