First and foremost, make sure you can remove the fill plug before draining it. Since you need to remove the shifter to pull the trans, you'll find it much easier to refill it through the shift tower while you watch for it to overflow out the fill hole. Also use the right fluid. Not GL rated stuff with sulfurs that will eat the synchros. Redline MT-90, Penzoil Synchromesh, or synthentic 10W30 motor oil (what most dealers use now).