Regarding the transfer box oil the problems grew from Vauxhall advertising. i.e they said that the box was maintinence free.
which meant that some owners never replaced the oil. Cosuquently the viscosity of the oil degenerated so became inadequate to
efectly cool the oil and so protect the the ram seal from melt down. When this occurs the power steering fluid which opperate the 4x4 system forces its way under high pressure and fills the gearing side of the box. This is why you have the pas oil forcing up the box breather pipe into the engine bay and onto the road. I have suffered this problem first hand and fixed the box myself with advice from Richard King founder of the Transfer box bible @
www.cav16. If any members needs to know all about the transfer box I urge you to go to this great site.
The secrets to prolonging it's life you should observe the advice about tyre tread etc because failure to do so puts more pressure on the box and will eventuly lead to destruction. The main strong advice is as in my case is to change the gear oil once a year and the box will go on and on happily gripping the road like a train on tracks.