Currently on a project which I'm managing, we installed a recirculation pump and pex piping in an open basement. The cost was $750.00 labor and material which included approximately 150 feet of piping.
Unfortunately without knowing the specific details of your project and layout of the floor plan and plumbing fixtures it is imposible to project a cost for labor and material. I recommend that you contact three local licensed plumbing contractors in your area to visit your site and present you with a proposal for all of the plumbing and patch work.
Good luck and say hi to Nancy for me.
For more information:
Read "Do hot water recirculation systems work? What kind would you recommend?" a Q&A answered by Kevin Burrell.