the heater is AWESOME you definitely want to keep it. I live in the south and it is still nice to have in the evenings and in the spring when it's cool.
Its exactly like a car heater, there's a box with a heater core inside and a blower on the side. I replaced my heater core this year with the replacement from heatercraft, it fit fine but I had to notch the box as the pipes were shifted an inch or so. Took five minutes to do that.
I pulled the footboard and plastic structure holding the heater box and put a sub box there, I am in the process of mounting the heater box in a better way for best access and function. If you pull the plastic structure and have an SX, put the screws back in with some sealant as the screws go into the starboard ballast tank.