After you flush the water lines until you have clean water running out of the faucets, be absolutely sure the water heater is full before you turn it on. If it's not full, the electric heating element will burn out in seconds.
Also, do you know when the fresh water tank was last sanitized? You may want to flush and sanitize it yourself. There are discussions about that in this forum.
2011 Sunseeker 3100
1997 Pathfinder Toad