I chased alignment issues with my blazer for a long time. No shop really knew how to do it correctly and after spending $100s of dollars I was probably better off trying to figure it out myself. If your alignment needs more than just adjusting the tie rod and steering, I hope they knows know how to correctly shim spindles and aren't using ball joint shims.
Changing leaf springs on a solid axle truck doesn't change the toe or the camber. They will be exactly as good as they were before the swap, and equally adjustable. If you bend the axle housing climbing rocks, most shops won't have any idea how to correct that. But if you just need the toe set it will be the same as any stock truck (TREs).

