mr.mark
12 years old! You are doing great! Throwing $8 or $10 at it now, and it IS simple to do...shouldn't hurt and could only improve the situation.
-IF electric, turn power off...gas?... turn gas off.
-Turn cold water supply valve off...none?...turn off main water valve to house.
-turn on the hot water in any sink...leave it on.
-now, the power is off, there is no pressure on the system.
-Remove the overflow pipe from valve
-remove the valve.
-Go to the local hardware and get a water valve of aprox. same size/same threads...and get some plumbers thread tape or goop.
-re-install and go backwards through this procedure. Run the hot water until all air is out of the system then re-light or throw breaker.
Should take all of 10 minutes either end and a trip to the hardware.
Do this yourself...plumber will cost about $100/dishonest $175...I charge $78
ola