Rex wrote:You could easily drive without 3rd gear for years.
It's a Honda, blessed with the ability to rev high but a paucity of torque...just drive it in second and shift at 9000rpm.
As to your question, if it's got a bad synchro it could last a few months or a few years...it's hard to tell. My 240SX grinds into 2nd when it's really cold outside.
Depending on how bad it is, you might be able to lessen the problem with a fluid change. Honda guys seem to like GM or Pennzoil (the Pennzoil is cheaper) Synchromesh for their gearboxes.
Honestly, if the transmission isn't complete **** when you drive it and the rest of the car looks decent, I'd take the Honda and ditch the Tempo. I had an '87 4 cylinder Tempo and it was, honestly, the worst car I've ever experienced. The engine was unbreakable, but the electrical system and most of the rest of it was complete and utter crap.