Pitman Arm Replacement on 1999 4WD Blazer

The Ole Blazer has steering slop and my local Mechanic, who happens to be a close friend, examined the steering system and told me I needed to replace the pitman arm. I went to the parts store and purchased a new arm and a Pitman arm puller. Once I had the Blazer on the jack stands and examined the "job", I cannot see how it can be replaced without removing the steering box. Has anyone performed this repair and can you give me some advice before I screw this up ?

You have it right, you have to remove the steering box out of the truck and replace the pitman arm. Three bolts hold it on the frame, the steering shaft has to be unbolted from the box, and the two lines. It comes straight out the front, with the front shield removed of course.

Thank you Blazes 9395, appreciate your help. Looks like an all day job....