Stove top gas leak (Russell Range)

Problem description:
I have a 6 burner Russell Range. I was smelling the light odor of gas coming
from the unit when all controls were off. I contacted the gas company and we
took the stove pieces off to expose all the burners. The gas man place some
liquid soap at the top of one of the burners and it created a bubble indicating
gas was coming out the burner when the control was off. He concluded the gas
control under the knob (gasket or similar) was leaking and needed to be
replaced. That appears to be the case but I don’t know what to order. Can you
assist me in 1) identifying the part(s), and 2) Is this something I need a tech
to do or if I’m reasonably mechanical I could easily replace myself.
Thank you.
Steve