First off, if you broke one it is likely the others are bad also. I would inspect all or just change them all. If you loose an important one the rig will come down or the mast will break.
I have never used a gage, just set them by feel. If the others are OK (which is unlikely) you can just snug the new one up at the dock. Then go sailing and set it so that it is a little loose on a starboard tack (opposite side). Sight up the mast while sailing to make sure the mast is straight under both tacks.
But please check all the rigging first.