Lost hydraulics on L175 Kubota

[Wilmo]

I was mowing 4 acres and lost hydraulics on my L175. I could not move the 5' Woods Finishing mower up or down, nor the front loader. I am going to try to replace the filter and hope that fixes the problem. Any tricks to replacing the filter? Does the fluid drain from that opening? If I have to replace the pump, is it an ordeal? Can a "non" mechanic do it? My manual does not show any diagrams on the pump. Looking for pointers. Thanks.