Christina, glad to hear you are having so much fun in the motorhome. You can and need to turn off the water heater and power to it. Use that hot water up or let it cool off. Then you will need to turn off the water supply. Remove the connection for the heating element and let the tank drain. Clean up any scale deposits left around the threads of the hole and on the element itself. Use a generous amount of teflon tape or pipe thread compound around the threads of the element and reinstall. Be sure it is tight and reconnect the eletrical connection. The power must still be in the off position or the power cord disconnected. Once this is done fill tank with water making sure it is full before returning power the the heating elment. You do not want to open the pop off valve on the tank. Let air accumulate at the top of the tank for water expansion when heated. Open a hot water side valve to verify it is full.
Your leak should be repaired.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7