The hardest part is usually getting the old hardware apart. With the rust problems here, I usually end up cutting them apart, sawzall and grinder. Impact can sometimes get them apart here, I usually start there and escalate as needed. The metal body mounts around here often need repair. I’ve bought large washers before to weld on to patch that problem. Or I’ll cut steel and make what I need. Annoying but not difficult. I usually replace the bushings with the body lift pucks, but again, rust and wear are a factor here that you may or may not encounter.
If you get poly body bushings, put a large flat fender washer between the poly bushing and the body lift puck, keeps them from sinking in. Same goes for rubber bushings if they don’t have a metal top.
E-brake cable mount on the frame up by the firewall where the cable comes down from the pedal in the cab needs relocated higher on the frame. That will have to be removed from the frame or the cable disconnected to do the lifting.
I’ve only done 1” and 2” body lifts so far. I never needed a steering extension or needed to change anything but moving the e-brake mount. I can’t speak for a 3” body lift.
I didn’t worry about the bumper gaps. With a 1” lift, the gap is minimal, especially on a first gen (which is what got that). My Choptop (2nd gen) got the 2” lift and since I had always intended on building custom bumpers, I didn’t do anything more than loosen the bolts for the front bumper and pull it as far out and up as the factory adjustment allowed.