Last time I checked a good immigration lawyer would charge around $3,500 for your application from start to finish. However, unless you have specific issues/problems it is very much a do it yourself process. Go to
www.cic.gc.ca and start reading (not the easiest website to navigate). Also go to the family class forum section of
www.canadavisa.com for discussion from people in your position.
If you have specific concerns you could book an hour for a consultation. This should be around $350/hr. We did this for advice/comfort on a specific issue and it was worth it.