Case 580CK: drain plug for hydraulic system?

I want to put fresh hydraulic fluid in my 580CK, and on many of the online fora the consensus seemed to be that there was a drain plug in the loader frame.

If there is, I haven't been able to find it! I hope someone can point me in the right direction, and also to verify that once I've drained it, 11 gallons is what I want to refill, given it's a standard loader/backhoe combo?

Thanks.

Case 580CK: drain plug for hydraulic system?