No, shocks are designed to dampen the rebound from the suspension and not provide support for the vehicle. The exception would be air shocks. These are generally used in the rear of a vehicle to support an unusually heavy load. You would not want to achieve a "lift" with these. Replacing suspension springs (coil, leaf, torsion) is how to get your SUV higher. However, this causes different geometry for the drivetrain and requires research to do it right.
Yes you can, i currently have longer springs and shocks that make up the 2in lift, no need for a transfercase drop too, i got it off of rustys offroad.
Yes... But it Depends on what type of vehicle you have... You may only have to purchase a larger (longer) set of shocks that will give you the lift that is needed for running bigger rims... OR If you cant find the size of the shock you need You may have to switch over to an adjustable set of air shocks if they are available for the type of vehicle you have. OR You may need to have a machinist/mechanic fabricate a set of shock extensions and have them welded into place on the vehicles underbody.
4 shocks ONLY, NO struts.
Turns the airshocks on/off, the only time you need it is if you're putting the car up on the lift. If you do not turn them off before lifting, the rear shocks will compress and the car will appear to have blown rear shocks until you start it and the airpump kicks on.
Only if the new number was larger than the old mean.
The body lift does not matter, it just lifts the body. The only thing you need to worry about is the length the new suspension will add to the stock suspension. For example if you put on a 4" suspension lift then you will need to add about 5" - 7" inches in the shock to make sure you have enough up and down travel within the suspension lift, and that it does not "bottom out".
Only if the shocks need replacement.
It does not have shocks on the front it has struts which should only be replace by a professional. The rear shocks are easily replaced. Just unbolt them and install the new ones.
The rear are shocks the front has struts. Rears shocks are a snap to change. Front struts should only be changed if you have the proper tools and knowledge as it can be dangerous.
A body lift raises the body of the vehicle higher above the frame of the vehicle. A body lift does not raise a vehicles frame above the ground (e.g. does not increase a vehicle's ground clearance) but it may allow for the installation of larger tires. A lift kit raises a vehicle's frame further above the axles by using larger springs (or lift blocks placed between the springs and axles). This not only allows for larger tires but it also increases the height of a vehicles frame giving it more ground clearance and better off-road performance. Beware, lift kits and body lifts raise a vehicles center of gravity and got this reason many states have body lift and suspension lift (lift kit) limits. Check with the laws in your state to find the laws in your state before making such modifications.
About the only way is to adjust your shocks
Lesabres only have air suspension in the rear, they will be a combination of air shocks with a coil spring on the lower control arm.