I changed mine at 130000, to be honest the fluid was still very clean, but there can be problems in changing the oil, to start you will need a gearbox level stick (like a dipstick, but you don't leave it in) MB fluid is the cheapest correct type of oil, around £8 litre x 9 litres, new pan gasket and filter, later cars like yours will not have the torque converter plug fitted so you will need to drain down, replace filter and refit sump pan re-fill with oil run and change again then run and change again, other problem (not uncommon) is the pan bolts corroding in the pan clamps usually one is affected (front odd one, can't remember which side) so get a new bolt and clamp and be prepared to struggle to get the bolt and clamp off after the head has snapped off, difficult if you are working on the deck, i got mine off by drilling down the side of the bolt and tugging and levering till the clamp came off, stud unscrewed easily from box, i fitted all new screws with a layer of copper slip and a small drop of low strength loctite on the threads. also noted that the gearchange was less refined that with the old oil and took miles to re-adapt and become smooth again.