manual gearbox oil change
In Australia the 300 series has an R380 gearbox the fill plug is half way up the gearbox on the right hand side,this is a torx T55 head ,you remove it, like pzwerner says no point in emptying untill you know you can get out the fill plug. Then remove drain plug I think that is 22mm at the bottom same side as the fill pug. Fill the gearbox untill the oil starts to flow out of the fill hole then re-fit the fill plug. The R380 gearbox has an inbuilt oil p/p and forced circulation,over here it is recommended to run auto trans fluid I actually run synthetic Auto trans fluid as it can take a lot more stress than mineral based oil. Regards from Australia :drive: