Yes, the mast is going to weigh near 1,000 Lb.
Something else to consider here in jacking and blocking a truck for repairs where the mast system is being removed is that you must either remove the counterweight from the truck, or block up underneath the counterweight so that the counterweight mass does not become dominant when the mast mass is separated from the truck.
If the counterweight is left on and there is no blocking under it, the truck might tip backward when the mast is separated. This is something that must be addressed properly before unbolting the mast.