1st off, sliders are for the rear of the leaf, NOT the front. The front needs to be a fixed point. Second, Lee sometimes over-exaggerates issues, there's zero problem with shackles. And especially since most shackles have urethane bushings, even with the longer moment arm they'll be stiffer than the shorter stock ones with rubber bushings. don't worry about a thing with shackles unless you're building a pure corner carver.
Hangers, $80 is an average price, you can pick them up dirt cheap because the install absolutely sucks! Many guys end up pulling the bed. And you can't use the excuse of hangers because they're cheap, because if you're paying $500 in labor, you could have spent half that on a set of leaf springs to lower the truck, did the work yourself (its CAKE), and pocketed the rest.
The front drop is also a walk in the park. You don't need a spring compressor or anything. I can't even stress how EASY the front end is to lower. You remove the shock (whopping 3 nuts), you remove the sway endlink (one bolt/nut), you unclip the abs wire thats clipped to the upper A-arm. You unbolt the two upper A-arm bolts, the entire assembly rotates downwards, you pick the spring out, drop the new one in, and reverse (just install the camber bolts in the upper A-arms instead of the stock bolts & shims on reassembly). I guarantee a shop will charge you at least $200 for the front alone. I'd do it for half that if you were local
Heck I just did a set of rear leafs for a guy for a pizza
Its THAT easy!
Save yourself the money, do the install yourself, especially if you've wrenched on bikes, you can turn a wrench on the truck. Sell the hangers, and find a set of leafs