Unless you are a licensed plumber or electrician, you will likely have to have problems in those areas handled by a licensed professional. You may be capable of doing many of the normal carpentry things yourself, but even those should only be done with a permit and with the proper post-work inspections and approvals by your community’s local governmental body. Dong major work without permits will come back to haunt you or a future owner (who will then come looking for you anyway – and don’t for a minute think that you will be off the hook for that work).