Can't help with depression as I suffer from anxiety but diet and exercise are critical to mental health. So watch what you eat and get active. Counseling helped me a bunch too. It helps to have a pro give you insight and perhaps change the perspective of how you look at things going on in your life. I used a Christian counselor and she helped me a ton. I also did a 12 step program called Celebrate Recovery that helped a lot. Its designed not only for drugs and alcohol, but also hurts and hang ups.
As to your job, ask for a special project to keep you busy. Could be cleaning up stock room, refurbing or detailing used equipment, painting the shop, making displays etc. Heck, it could even be calling existing customers and offering a service special.
Good luck