You sound on track. For the ultimate in satisfaction
add a drain plug, I drill a hole in clear corner,
weld a fine thread nut to inside of pan. A fine thread bolt, washer, and
rubber washer make up the plug.
The play is, when you drain trans, you only get a little out, unlike an
oil change, most fluid stays in transmission circuts. If you change fluid,
be prepared to do it again in a few hundred miles. Mobil 1 synthetic trans
fluid is a
great way to go. Change after 500 miles, than once a year, after about 3
change outs, you'll be amazed how good fluid looks.