engine block heater

rv tech found my problem of kicking breaker out while hooked up to 30 amp outlet. they first thought that it would be the water heater element, after isolating it, the breaker still kicked out. they continued unhooking things with no luck. took the engine block heater out of the circuit and every thing works fine. I am not sure how to check the block heater out. just curious as to how big of a deal it is to change it and if I would lose much antifreeze in the process.
I have a 2005 H/R Scepter with a cummins 400 ISL.
Thanks in advance for your advice.