I’m Thinking Of Making A Career Change- I Just Turned 40. Is This A Wise Choice?

I have been a truck driver for ARCO for a few years now. It is a good job but I find it boring; Maybe I feel that way now that I have just completed my second deployment to Iraq with the National Guard- that was definitly not boring. I have an oportunity to get into law-inforcement. I wonder if I am thinking about changing careers too late in life and perhaps for the wrong reason.