I think my transmission has sent me a message.
My car only has 40,000 miles on it and its 18 years old.
But yesterday my reverse gear stoppped working.
Should I look for another used car or pony up and replace the trans for $600?

just get a used low miler tranny from a junkyard

Are you sure the trans fluid is up to the right level? It's not leaking, is it?