Power steering problem

[charger Downunder]

Thought this was a simple job took of the castle nut on the input shaft end and pulled out center piece and put on new o ring seal to stop oil leak, put  back together when i start the car the steering pulls hard to the left.
Turn car off raise it on stands and its very very hard to get the wheels to go to the right. Would this be air in the system.

Could i have done up the castle nut too tight.

I didnt touch the control valve on top of the box at all so i should'nt have to adjust it.?

Maybe time for a rebuild 93,000 miles. ?