I'm having Eibach lowering springs installed for $250 plus $79.95 for 4 wheel alignment. As for the DIY for springs, uh uh.
Good luck with that one unless you are talking stock springs. I replaced my entire 280Z suspension in a side yard in NY. And I wouldn't consider this. Once you see the springs you can tell that unless you have a spring press you aren't going to get these things installed. I have spring compressors and they don't fit.