I bought a double wide home 5 years ago and will admit with great shame that I have no idea how to maintain the poor abused air conditioning system.    
  
When I got the house, they had two filters stuck inside the 'closet' just sitting on top of the two sides of the evaporator coil (I had to google to find out what that's called).    
  
I can tell that's not how you put filters in an AC, but I can't tell you where a filter is ACTUALLY supposed to go, and my family keeps coming and putting filters back in there like that (see photo).  I assume a filter should actually go on the panel door, but it's very thin and filter won't attach to it.  


This AC has been through it.  I have 12 cats, and I'm pretty sure a teenager projectile vomited in here at some point in the last 3 years, and just pretended he didn't.  

I decided to bite the bullet and try to clean this disgusting thing and ended up using a shop vac to vacuum slimy black (mold?) off the top of the coil.  It was pretty significant but came off easily.  For the rest of the surfaces, I don't know what's safe to touch, because I literally do not know what this thing does.



So, the questions:

1)  Where does a filter even go?

2)  How do I PROPERLY maintain this AC system?  (And please assume I'm 5 years old.)

3)  There is a lot of nothing space above this coil.  Probably a metropolis for spiders and a portal to hell.  But I'm super tempted to try and stick a UV light up there to shine down on the coils to at least inhibit some mold growth.  Is there any "smart but super dumb" reason I *shouldn't* do that?



How do I do ANY of the things for this AC unit?