Some of the earlier trailers have stand alone converters and a separate power panel, whilst most newer models include a combination converter/power distribution panel with a/c breakers and dc fuses. These are a little more labour intensive to replace than the stand alone units, because of the additional wiring changes.

Both types are remove and replace items, with little modifications necessary to address in the installation. You will have to determine what type you have, and the model type which will give you the rating. An older unit can be upgraded with modern battery maintenance, instead of the old type of simple battery chargers.

There are various sources on the Internet, and you can usually match the ratings and physical sizes to closely match your present installation. It can be a DIY project if you have a basic a/c and d/c electrical knowledge.