I did an add-a-leaf on my truck, front springs looked a little worse than yours. The installation is pretty straightforward, with the exception of the change you will have in camber when you are done. How are your tires wearing currently? This is a good indicator of two things: when your truck was last aligned, and how worn out your front springs are.
Here's what I would suggest: get yourself a straight edge that will fit nicely on your front rims, and a magnetic based level with a pointer on it (harbor freight has them very reasonable). Now park your truck on a nice level piece of cement. Measure the camber as close as you can and record it. Now look at the upper ball joint camber spacer and note the degree offset and position.
After you install the AAL, measure it again and see if you gained a significant amount of camber. On my truck I went from almost zero camber to about 2-3 degrees postive camber. My tires were pretty worn, so I drove them around and looked at the tire wear and the outer edges of my tires were chewed off inside of 1000 miles. That's when I decided to look at my upper ball joint bushings and found that by turning them 180 degrees, and swapping sides, I was pretty close to zero again. After I completely rebuilt the D50, I changed the bushings to what I thought was as close as I could measure and so far my 35s are wearing nearly perfect.
Or you could ignore all this and pay somebody to align it. I was quoted $250 per side plus parts, so I decided to play around and try to learn something.
Good luck