Well, we spent the morning on top of the trailer -- got the plastic shroud off of the a/c unit -- and the layout of the components looked nothing like what I had seen on YouTube! (And I watched several hours of videos, prepping for this job.)
The evap coils were inside a well-sealed inner box -- fastened with clips -- and there was a lot of foam rubber glued to the box, making it very difficult to remove the plastic box. So we didn't do anything to the evap coils -- never even got a look at them.
The condenser coils were much easier to access -- they wrapped around the back of the whole a/c unit. (This is a very small Dometic a/c unit, much like the current Penguin model.)
But the condenser coils were clean! Just for fun, we vacuumed them and used an air compressor to blow away any dust -- but there was hardly any dirt.
So, now we will test out the a/c and see if it still ices up (as it had been doing). If it does, we will call a mobile repair guy. We gave it our best shot, and there is nothing more that we can do by ourselves.
There is a time to boldly DIY, and then there is a time when discretion is the better part of valor.
