Hello, Rita,
I have a Majestic here that I found at a yard sale a couple of years ago. It has a "butterfly" point and a visulated section. It needed a new sac when I got it. The section on mine is not threaded into the barrel.
If the sac is OK, you can clean the old ink out by operating the lever and filling it repeatedly with water. Invert the full pen a few times to make sure you rinse the entire sac out. Do that until the water runs clear and you should be good to go.
You only need to operate the lever once to fill the pen. Lift the lever until it is perpendicular to the barrel, immerse the entire nib and part of the section in ink, flip the lever back down into its barrel slot, and wait ten seconds. Remove the pen from the ink and wipe the section and nib with a tissue.
If you ever need to have a lever filler to be super full - I mean, full right up to the gills, fill it once the normal way and then hold the pen nib-up and tap it a couple of times to get the air bubble in the sac to come to the top. Then slooooowly and carefully lift the lever until you see ink well up around the base of the nib. Then dip the nib and section into the ink again and lower the lever. It is best to do this over the sink and wear rubber gloves! (and maybe a raincoat)
Rusty clasp? Cleaning methods depend on how much rust there is and how deep into the metal it goes. If there are just a few, small, lightly rusted places, you can scrape them gently with a screwdriver blade, being careful not to scratch the good places. If it is rusted pretty much all over and there is not enough original finish left to bother with, I would use some fine steel wool, followed by polishing compound (plain white toothpaste works well sometimes).
Paddler