Struts won't cause sag but springs will. Just grab a tape measure and check the differences in height from each wheel arch to the garage floor. If the rears are lower than the fronts, sag.. If 1 rear is even lower, reach in there and feel for a broken spring. An old CEG'er showed me this trick.
Special tools..18mm 1/2" drive 6 point socket, 1/2" drive breaker bar and a long pipe to crack the lower strut pinch bolt. Also an 18mm box end wrench and a 6mm allen wrench for the spring perch. You have the spring compressors so the rest is just standard stuff.
