Hello, "SteveDeal," preparing a patent application to protect your Innovation of a mechanical lock coupled with an electronics module does lie in my area of expertise. I've been a Patent Attorney for almost twenty years, with another ten years previously as an electrical/systems engineer
There are two ways of initiating the patenting process - Provisional Patent Application (good for only one year) and the regular Utility Patent Application. It appears that you may be thinking of the regular Utility Patent Application. The Patent Office will charge a filing fee of $530 to file your patent application.
Based on the technology inherent in your Innovation, I estimate at least three weeks of preparation required to fully cover your disclosure.