Hydraulic External Steering Problem - Educate me
 

2002 Baja OL twin 496 mags (non HO) Latham external hydraulic steering. I do all of my own maintenance so I know my way around my boat but I do not know about power steering systems. Lost power steering yesterday. When steering wheel locks either direction loud sound coming from steering wheel. Sounds like the pump is struggling? I looked in the reservoir and there was foam on top of the fluid but it was still full. I am not sure if the foam in the fluid is new I've never really noticed it before though.

My questions:

1)is the boat still safe to drive? Steering still operates fine it's just difficult to turn the wheel.
2) any thoughts on a diagnosis and potential repair?
3) how do you replace the hydraulic hoses on the transom exterior and when done anything special need to be done ( evacuate the system for example )?

THANKS GUYS!!