DO NOT FLUSH THE TRANSMISSION!!! Doing so seems to lead to problems. I have changed both my VX's to Amsoil Synthetic with no problems, one at 103,000 miles and one at 150,000 miles, but I sure as heck did not flush them! A filter change can only help...
lol yeah dont worry ive heard nothing but horror stories about high mileage flushes
IMHO, running the tranny through the gears with no fluid in it to push out every last dribble is a really bad idea too. Just drain out what you can and fill her up again.