Multiple Issues

Hello, I have a couple of issues with my explorer. The first is the AC Compressor is knocking when turned on and still knocks a little being off. I figure the compressor is going out and I was wondering how bad this could get as far as operation of the vehicle. My other is the Power Steering pump. The pump constantly grinds even when the vehicle is still. It grinds and vibrates really loud when turning the tires. It still grinds when driving but not as loud. The Pump is full of clean fluid. Also, When you put the explorer in gear, it revs up for a sec and drops and sometimes it kinda****** very little. Is that normal?

Thank you,
Rob