Adel
If you use the search facility using key words like "trailer bearings" "bearing torque" you will come across posts with hopefully some relevant and informative information to help you.
I have not had to change my trailer bearings on my previous trailer but i do remember reading about the shaft nut being a "one time" use and when you order the new bearing it comes supplied with a new nut which has no split pin to lock it onto the shaft, just as your old one. You will need to tighten it to a specified torque which from memory was quite significant.
PS
Hope the stains come out of your drive ok.
Peter C
