Although the gearbox has never really given me many issues I felt, whilst it was out I would change the oil and give it a clean up. I started by using POR15 Marine Clean to remove the majority of the grime.
After a fair bit of elbow grease and buckets of water the results were apparent. I decided to treat it to a lick of paint.
After one/two coats I was very happy with the results. I also changed the clutch plate and oil (type 9 5 speed takes about 1.9litres) In most cases, get the gearbox as level as possible and fill it until it pours out of the hole. More info can be found here: Click Me