Applying at a place I used to work?

I left my job with a local govt about 2 and a half years ago because they were changing the scope of the program I worked with and I didn't feel super safe (I had to do inspections of clients homes). So I looked and found a private group that paid much better. But, it also meant weekends and a little longer hours and fewer holidays. Plus, the kicker-the person I was supposed to replace in 6 months decided not to leave and he is realy negative person who makes the whole office miserable. So I saw an add today for a position with my former place that is something I would like and have had training for and could do. Plus back to a M-F 9 to 5 hour for lunch, all holidays off and great benefits. So, should I apply and how do I do that short of saying "I made a mistake and want to work for the government again". I did leave on good terms and the person who replaced me was someone they re-hired after leaving 7 years prior.