are you kidding ? tbh if your tech cant work it out on a 99 car i would say he isnt fit to work on the car.
undo the nuts at the top of the rear shocks, the rear axle beam should then drop down. Next pull the std springs out (pulling down on the trailing arms if reqd) then refit new springs lower car down so the tops of the rear dampers pop through the holes in the rear quaters, replace the nuts torque everything up and youre done. if he has a ramp should take no more than 15mins