In addition to the REVERSE POLARITY FUSES mentioned here there is usually an in-fuse or in-line circuit breaker installed very close to the battery terminals.
These are the three main protection items to prevent damage to the trailer system when the battery terminals have been accidentally reversed.
Be sure to correct the battery wiring before replacing or resetting these three areas of fuses/circuit breakers. Otherwise they will just blow things again...
Don't feel too bad - It happens to the best of us...
Roy Ken