Disclaimer: Neither TOCAU nor I take responsibility if you damage or blow up your car in any way. Do this DIY at your own risk!
Time to change that gearbox oil? This guide will show you how
Things you need:
Bucket/Drainer for oil
15/16 Socket and wrench (ZZE122)
17mm Socket and wrench (ZZE123)
"Size 30" Allen key with wrench (ZZE122 Ascent/Sport/Levin etc.)
Gearbox oil of your choice (refer to owners manual for recommended weight) + Nulon G70 Additive 125ml (optional)
ZZE122 5 spd takes 1.9L
ZZE123 6 spd takes 2.3L
Floor jack and jack stands
Dirty Rags
Muscles
1) Use the floor jack to jack up the car from the front.
2) Place one jack stand on the drivers side of the car and lower the car. This will help you get access to the sump plug from under the car.
This is the sump plug you are looking for...
Use the 15/16 Socket to remove it and let the oil drain, in my picture the oil wasn't dirty or used much (you are meant to change every 50k or 30k if you operate gearbox in harsh conditions) but for the sake if this guide I have done it again as I needed to replace the unknown oil the mechanic used to replace when they inspection my car during insurance work.
if the oil is black and runny like water, you BETTER CHANGE IT!
this is what the gearbox sump plug looks like
After finished draining, bolt the sump plug tight (just nip it up, no need to superman strength) and remove the jack stands and lower the car.
If you have the 5spd manual you are to remove the filler plug circled in red with the size 30 allen key.
If you have the 6spd manual you are to remove the filler plug circled in green with the 17mm socket wrench.
(Thanks to Superdave for the picture 
)
I only took a picture of the 6spd box filler plug, the other one should be clear from the picture 
depending on your gearbox, you have to fill up with the correct amount of fluid...
AGAIN
5 spd gearbox = 1.9L and USE THE ALLEN KEY FILLER PLUG
6 spd gearbox = 2.3L and USE THE HEX FILLER PLUG
If you are using the additive, Put in 1L of fluid first like so
and then squirt the G70 inside
then fill up the rest of the oil to capacity, taking care NOT to overfill the gearbox with oil!
Once your done just clean up and replace the filler plug where it was and enjoy smoother shifting!
Enjoy! 
