i replaced my steering box in my f-150 several times. i purchased it from advance. the replacement was a remanufactured one and the first one i put in had a problem with the return line connection. No matter what i did there was a small leak at the connection. I brought it back and had it exchanged and put the new one in and no problems.

it's pretty easy to do. you slide back the plastic cover, remove i believe 2 10mm bolts that connect the steering column to the box, remove the 2 pump lines, remove the pitman arm (you can rent pullers for free at most parts stores), and then there's 3 bolts (i think 18mm) that attach the box to the frame. it's pretty easy to do.

the box is pretty heavy so you might want to have a helper when reinstalling it to hold it in place so you can get the bolts in.

also, you'll need to jack up the front end when reinstalling and prime the new steering box before firing it up.