It should be the right part, if there's visible wear in the shaft you may leak, otherwise it will be fine when fitted.

To fit (I find it easier to just remove the box rather than do it in the truck) remove the pitman arm from the box. Pry out the old seal (can do this with a self tapping screw through the seal and pull out with vice grips). Any oil left in the box will now pour out. Clean the shaft and seal area, you want it spotless (so you don't drag grit into the box).
Now you can slip the new seal over the shaft, you should dip it in fresh power steering fluid to help lube it on. Then gently tap it home into the steering box body, work around the edge so it goes in evenly. Reattach pitman arm (there's a line on it and the shaft for alignment.
Then refill your power steering, and with the engine running turn it lock to lock a few times to bleed out the air bubbles, and refill