My ST300 would slip freely when I didn't keep the fluid at a reasonable level. I'd think it was failing then remember to fill the fluid and it would work fine again. It still shifted softly (they don't call them 'slushglide' for nothing) but 190,000 miles on the original clutch pack will do that.

The ST300/'Glide became the transmission of choice for drag racers in part because it is pretty stout. At very high horsepower levels the Al case can crack but the internals are pretty bulletproof for the majority of street applications.

I second the 'fill it and try it out' approach. My car had been sitting for about 2 years when all the tranny fluid dropped out - the seals dry up when they're not used. I haven't re-filled and tried it out yet but am expecting it to still be working.

I would not consider transmission removal from ramps. Use good quality jackstands at the corners.