You don't need to paint it, though IF you do, use a flat non-glossy paint, such as a dull gray, or cream. IF you use the CLR, make sure you have good thick chemical proof gloves on, and perhaps a respirator.
Those prices I quoted are for brand new equipment. If you can scrounge some, or get donations, it would of course be cheaper. IF I was YOU, and didn't know as much as I do about these, I'd be inclined to take a LOT of photos of it, post them HERE, and ask more questions about IF we think it's restorable.
The very FIRST thing I'd do, is make dead SURE the mounting pole is absolutely level, North-South and East-West. IF it isn't, you need to fix that before you do anything else. IF you can't, it'll never be right, and any money will be down the rat-hole.