26 oz. of oil - you can drain the mechanism easily enough by laying the machine with the drain plug at the bottom of the transmission housing facing down, remove the plug and filter screen and allow the oil to drain out, then turn machine over so plug hole is facing up and replace the oil.  Many use air compressor oil as a suitable replacement, a few have experimented with synthetics with good luck too, but it needs to be of lighter viscosity to allow the oil pump to get it up to the top of the transmission shaft.  

The pump may be a hard find, where is leaking from exactly?