No experience with just replacing a valve body either, did the whole thing at once, but you may want to consider a torque converter real quick if you haven't already replaced yours. Several problem reports I've read here and other places have said one of the primary causes of transmission problems is the torque converter starts slipping and the damaged material then takes out the transmission and the valve body. I'd hate to think of upgrading the valve body and then having it ruined by a failing torque converter.