hi
irrelevant of age and mileage, if it were mine I'd give a full service, change all the oils and service parts, at least you know it been done and forget about it for a while
I would on use genuine zf part for the gearbox, as using non zf oil can cause lots of problems, service kits are avail on ebay that include pan/filter, new bolts(updated type), new mecha sleeve( prone to leaking and oil zf lifeguard 6.
dont forget the diff, often overlooked, spark plugs as rears require intake manifold removing, which means only front sometimes get changed, also fuel filter and pollen filter
if you need any manuals or info, have a look here http://www.jagrepair.com/
cheers
Joe