lift kits cost alot of money more then what they say alot more to it then swaping the springs and shocks the rest is not a problem and not cost to much
Depends on why you want to lift....
You can do the suspension stuff - the main aim of this is normally to increase ground clearance for the chasis & body and usually you get a bit more axle articulation as well so that the wheels stay on the floor - however the differentials remain at the same height so ground clearance isn't improved for them.
You increase diff ground clearance by fitting bigger diameter wheel/Tyre combination.
To do this you can either do the expensive suspension stuff, or simply raise the coachwork off the chasis which is much less expensive. Both give you bigger wheels which gives a more aggressive look.