Puma 1700 - couple of questions

[rovermorris999]

I have a kit car with a mid-mounted 1999 Puma 1700 Sigma engine. Couple of questions - what does the gearbox drain plug look like? The Haynes manual is less than uselss and it's not easy to see on the car as the the engine/gearbox is the 'wrong' way round, with the exhaust at the back. Is it a hex nut or a recessed allen bolt? There are one of each that it could be.
Secondly, how long does the orange antifreeze last? It's been tested and is ok for frost protection but I'm more concerned about the anti-corrosion additives. The car has done 6500 miles over 5 years since it was last changed as far as I know.
Cheers.