check the colour, check the coolant DOUBLE check the coolant level, the bottles discolour over time and look like they have the right level in them.
Drive it 20-30K and vis check the coolant in the surge bottle and the oil again.
if it looks good have at it,
i also reccomend checking for leaks and temperature the diff, the portals, the transmission power steering fluid and if fitted the clutch housing PTO.
keep it at 75kph if you dont want to hurt your wallet too badly.
DONT race the 4/5 change, keep the clutch all the way in and do it in 3 distinct motions of the lever on a 1 count.
into neutral, across the gate into gear. you can skip up if your unloaded on the flat and do a 4/6 change but I prefer a 3/5
Use the exhaust brake but generally dont bother once your in the bottom 3 gears.

