good news is you can fix 5th gear easy enough
as rudey said though, thats spot on info
btw i average atleast 1 box a year,,,,,,,,,, and thats on my runabouts, the cossie box is fooked in mine too but the T5 is a trooper and just carrys on going
take off the end and have a play, ive got a box with a fooked lay shaft bearing but its still got 5th on it,,,,,, actually ive got 3 like it