To bad they were not lowers our stock uppers are not to bad. But since you have them I would use them also. UNLESS you want to find a trade or sell them and get something else.
But since you want to install them it is a breeze. It is failry easy with the back end of the car jacked up. or even if you decided to take it somewhere it would be cheap!!
Jack the aft end by the body on both sides. Put it on jack stands move the jacks to the axle and jack the rearend to support the weight and take one side out at a time and replace. Pretty simple. the hardest thing sometime is just getting the hardware back in. DO YOU HAVE A B.F.H Big F&*%ing Hammer HAHAHHAHAHAHHAHAHAHAHAHHA