2001 Ford F350 Power steering

I have a 7.3 L diesel 350.

It is new to me and is needing lots of work. The power steering was leaking and making a bad whinning sound when turning. I had the power steering pump replaced and flushed, now there is a slight whine to it but it is real hard to turn when sitting still or when it is cold in the morning.
When moving it turns easily. The whine is very slight now. Someone mentioned to me that hydro boost might be bad. The brakes work great.

What is next for me to repair.

I also smell a diesel smell when I run the cool air vent. I can't tell if it is raw fuel or exhaust that I smell. Only when I have the fresh air vents on. What could this be, we just replaced the fuel filter to see if that would help.

I have auto 4WD switch in my turck. Do I need to turn the hubs to go into 4wheel low. Which way is lock and which is free? Does counter clockwise or clockwise work?
Thanks,

mh