You do not need an agent. As long as you have a Thai wife and she has a housebook in her name she can assist you to obtain a Thai ID and yellow housebook,
You are certainly not onm a Retirment Visa. Your Retirement visa expired 2 years ago. I suspect that you are on an extension of stay based on being over 50 years of age.
Chiang Mai Immigration has a large scale listing on its notice board so that you can take a photo. Or they will give a one page print out. If they do not have a list, I do not see how they can tell if your application is complete.
If you overstay by a couple of days: 1. If you submit to Immigration and pay the designated fine, probably no further problem. 2. If you leave the country after this overstay, Immigration may put an overstay stamp in your passport which may cause you problems if you subsequently try and reenter Thailand. 3. If caught by police or Immigration (maybe even on your way into the departure airport), you would be subject to a prison stay, a big fine and excluded from reentry into Thailand for an extended time. It is never worth overstaying.