I don't get it, do you think it's dead because it's low on fluid, or was the fluid dirty? I change my filter and fluid in the pan every 50K miles (have done it twice now) and "knock-on-wood" am on my original trans which still shifts fine.
I would NOT flush the trans, only change the oil in the pan and put in a new filter. That's a debate I know but I was always told it was a bad idea to flush an older transmission, better just to do the pan.
One other thing, they no longer make the correct fluid for our cars, so make sure when buying new oil you look for the Dex made for OLDER GM cars. That will be printed on the bottle. I recommend Castrol high-mileage, I like their stuff, but if you can afford it I hear Royal Purple is great too.
Good Luck!
-Mike