The LP lines may just have a "tee" connecting the two tanks. This isn't the best now days as both tanks will drain and you could run out of fuel. The auto transfer regulator can give you a little warning that you have used up one bottle and has switched to the other.
The hoses are the old style. if they are in good shape with no cracking I wouldn't worry too much about them.
My old rig had the red knob. It was tight even when it was new. I would be very careful about using any solvent type lubricant on it. Maybe a little spray silicone, but nothing like WD-40 or Liquid Wrench.
