Hi Rob and welcome to the club, with reference to the auto, when the little button is pushed "IN" then you have engaged the O/D and it would act like a 4th gear, there should be no lights on at this stage.
If you do a search on "Supra chat", "Tech ref", you should come up with a LOT of talk on the Auto box, I'll just put up a few things you may not be aware of.
There should be a manu button at the side of the stick, which when pressed allows you to use the auto shifter (and box) in nearly the same way as a manual ie go from 1 - 2 - 3 when you select it, (good for playing).
There is also a kick down button underneath your go faster peddle, when you go to WOT (wide open throttle)the switch will drop a gear and you fly, (oh, a little anyway, forgot you have a N/A).
Hope some of that helps, sorry I can't shed more light on your problem light.