I'm thinking about picking up a pump because I just can't take the heavy steering when stopped.. Being as it's used, the only thing I need to do is change the O-ring inside the pump? And to prime it I think I need to lift the front in the air and turn the wheels back and forth?

Pumps are self bleeding as you move the wheels.  

 

If you pick up a good used one with no leaks, you should be good to go.

paypal $35 and send a shipping address and i'll send you one.

what he said - no need to bleed, they're simple.

 

that being said - are you sure it's the pump?  i would expect the ujoint more than the pump. i have one of those too, got it from Imdew ironically enough!  shipping and it's yours.

I know it's the pump because it ran dry, and no longer works when filled

That could just be the pressure relief valve.

These are so cheap to replace used and so easy to remove its hardly worth messing with the old one though.

When I swapped out a P/S pump years back, I simply removed and replaced. filled the reservoir with ATF, turned the steering wheel lock to lock multiple times, and the job was done. I sourced the new pump from a yard. It worked great for years.

 

If your simply leaks fluid out, I have read others have replaced the "O" rings to fix the problem. I have not done this, so no comment on how difficult this may be.

Dealer sells a reseal kit for pumps is fairly cheap and takes about 20 min to install the most important is the shaft seal is last part in pump but were most leak