Hello, A 1998 Toyota Camera Trans was topped of with motor oil instead of Dexron. It has been driven some 2000 miles. Dip stick shows NO red color. Car has 160,000 miles. Trans has never been serviced. Should I drain, pump down several times and change filter or just leave it alone. One shop said to do nothing, it's to late. Just drive it until it quits and buy another car.

Well, too late to flush it since you've never serviced it. That may spell disaster. What I would do is drain and fill every 500 miles. It only takes 2.5 quarts when you do this, so this way you can do a little at a time.
There is a 10mm hex drain plug on the trans pan. You need a allen socket, not an allen wrench, and a long handle ratchet for leverage.
You can strip these drain plugs if your not carful. Never mind the filter.