no issue, with half level u can do a cross country trip, gear oil it cheap, get 1 ltr bottle from total or caltex 85w-90 shud b suitable...
on the other note, do u know when was the last time gear oil flushed? if no then its good time to get it flushed and pour new gear oil...
- get the reverse switch fixed
- place a tube over breather hole so that water and moisture does not enter
- get the drain nut checked for leakage or replace it.
get 2.5 or 3 ltrs of new gear oil and goto any good oil change facility, they will drain oild old and pour new oil..
the gear shifting shud improve and gear will be applied with lesser force, any excessive sounds due to worn out oil shall gone and life of gear box shall be extended.
do watever u want but never listen to any mechanic who says ' gear oil jitna purana hota hay utna hi acha hota hay'
gear oil has life max to 40k kms or less...
sometimes people while selling the car put thicker oil in gearbox to mask any unusal sounds, sometimes they put bananas or woodgrains as well...
if such is the case then u might experience some unusal sounds, but not likely