A Career In Law Enforcement

Greetings Everyone, As the title states I am seriously considering joining the police force in either the municipal or county capacity. I am a 27 year old Marine Corps Infantry Veteran currently in school studying Constuction Management. It seems like a great field of study that pays well but im just not feeling it. Are there any of you in law enforcement now that have any advice for someone like me? Am I too old to pursue a career in law enforcement? Should I switch majors and steer it more to the law enforcement side of things? Or will my veteran status be enough experience to get hired? Any thoughts are greatly appreciated.

Edit: Thank you to all who replied, all of your advice, and words of wisdom. I really appreciate it.