That port is just a port connected to the battery. You will need a charge controller and a solar module to connect to it, you don't need a control panel in the trailer. The Zamp port uses an SAE plug but with the polarity reversed from normal (Zamp did that to try to get you to buy their solar kits). But you can buy any solar kit you want, just reverse the polarity of the output of the charge controller in the kit. Or you can connect a solar kit directly to the battery and not use the Zamp port. For safety, you should also add an inline fuse at the + terminal of the battery, either to the + wire going to the Zamp port or to your kit directly. A 15A fuse will be fine.
There are lots of choices in portable solar modules. If you get around a 100 watt kit (pretty common) you can run most most 12V things in the trailer as long as you're frugal in your energy use, the weather is sunny and the solar module isn't shaded at all. Get a long cable so you can place the solar module in a sunny location. You won't be able to run either the fan or the heater for long periods, and of course your ac appliances won't run. The slide is fine, it only runs for a few seconds so doesn't use much energy.