1996 Cadillac Seville bushings

Hola;
I'm in need of bushings for the rear suspension of my cadillac seville sts 1996. No one seems to be able to help. Some tell me that I need to buy the complete part lke the knocle, lower arm etc. Do they come separate and if so are the after market better than the factory where can I buy them?
2) how can I tell if the electronic suspencion is working, will the shocks go low or how do I know that I need to replace the shocks. They are so expensive. This is electronic suspension.
excuse my ignorance on this matters but I need help. I love my car and do not want to part from it.
thank you.
jose quinones.