Its not all that difficult to DIY this job. Just make sure you have some time and patience. Jim's right, might as well replace the bushings while its apart. This tech article should help alot:
http://www.pelicanparts.com/techarticles/911_suspension_bushings/911_suspension_bushings.htm
Waynes book was also a valuable resource when I did this a couple weeks ago. When you get in there, you'll probably have more questions. At that point, you can use more specific search terms to find a better answer on this board. When you get to the point where you are putting it back together, Will Ferch and Thom's (widebody911) spring plate calculator can save you alot of guess work. You find it here:
http://vintagebus.com/cgi-bin/spring.cgi
You will have to know (or guess right) the weight of your car to use the calculator though.
There is plenty of info on this subject in the archives of this board. I probably did 50 different searches through the course of the job, and only once was I not able to find what I was looking for.