Hey Guys, what is the maintenance intervals for a MK1 5 speed transmission fluid? I do not know if or when the previous owner has ever changed it. It shifts fine, and I am not having any troubles, so should I worry about it? Thanks in advance!

 

Also, what are the spec of replacement oil. I know 75w90 but dont know the specs

 

Last thing. Ive been reading that the drain plug is removed with 14mm hex wrench, not the 16mm 12 point tamper proof bit. is this right? Also, how do I know which one is the fill hole? any tips? Thanks again