I did my own core replacement last summer.  If you are considering doing it yourself, there are numerous accounts of the process in posts on the FSSA Facebook page.  I found them very helpful.  You may have to use a search tool to find the old posts.  You can also download instructions from our boat builders' website.  As a former carpenter/cabinetmaker, I owned many of the tools that would be required and had some experience in restoration work and the use of epoxy and associated additives.  Still, there was much to learn and the work was a bit of a challenging endurance test.  In the end, it was a success and my satisfaction has cast a different light on the darker moments of the process.