Hi Jeffo,
I would need more information about the age / year of the caravan, but yes, the boiler does need to be drained fully, using the yellow handle.
Depending on the age, and if an onboard tank is fitted, then this will either have an external drain valve or an internal drain plug.
The pump needs to be run "dry" for a short while, to expel all water, and if fitted, the pump filter should be removed, and again, the instructions on how to do this will depend on the age of the caravan.
The exact instruction can be found in your handbook, but if you need any more information, please let me know.
Thanks,
Ash