I can't really follow what you mean, but the gear that's right beside 3rd is second. Second is on the same shaft as first. The gear that's on the same lump of metal as 3rd is 4th, joined with the speedo worm between. So in short, if you have teeth missing off 3rd gear, and chips on second the only salvageable part of tour box is 5th.
5th never breaks so you havn't got much of value let by the sounds of it.
Post a pic of the guts of the box and highlight the chipped tooth to be sure.