Hmmm...no gain pot on mine. See the attachment for wiring and basic info that I used. I am guessing yes, either turn it way down, wire around it or add a attenuator. I get plenty of gain with mine. You will enjoy this, I asked the fellow selling it if it worked? He grabs the mic, slides the neck up and down, and says, "this part works!!!"
BTW, I can say with the utmost conviction you will absolutely LOVE the K3! I have had several rigs in my ham life, but nothing compares to this. I am a casual ham, but decided that when I turned on the rig in the evening or Sun. afternoon wanted to be able to hear other stations and them hear me. All that and so much more is true.
Are you building or getting a pre-assembled?
cleve/W5CEM