hmmmm....i dont think that the problem is the gear oil, although you could give it a try first to spend less.
i do believe that your problem is the gear synchronizer for your 1st and revers gears. bale i-isa lang po ang synchro ng 1st and revers gears, isa lang din sa 2nd and 5th at isang synchro para sa 3rd and 4th.
if im correct and the problem is the synchro, malamang pudpod na ito or sira na kaya mahirap mag shift nang gears. if thats the case, pray hard na merong binebentang synchro lang, minsan kasi, yung synchro, may kasamang gear na and it makes it more expensive.
synchro + 1st gear: 8K
labor: 2.5K
gear oil: 3 liters * 150 each
