Glucosamine may very well improve the health of joint cartiledge, but when you have bone-on-bone wear, the cartiledge is GONE and nothing will bring it back. A variety of things may help with the pain, but the only way to repair it is joint replacement. The longer you wait, the less you move your shoulder, and the more "frozen" it becomes, making the surgery and full recovery of function more difficult.
Anyone who has had joint replacement surgery will need antibiotics before having further surgery or dental work. That's the only medication. The components are totally inert; chrome-cobalt alloy, stainless steel, or titanium, with high-density plastic bearing surface. Some hip joints are metal-on-metal or ceramic on metal, doing away with the plastic component. Shoulder joints aren't weight-bearing, so they just don't wear out. Total joints do set off metal detectors at airports; you might have to show them a letter from your doctor and your scar.
Shoulder joint replacement is less common than hip or knee, but is usually very successful (if performed by a competent surgeon). Recovery and rehabilitation are usually quick, although repair of soft tissue injuries like rotator cuff tear may make rehab more of a challenge.
The longer you wait, the more pain you will experience and the less use you will have of the arm. Pain will become the focus of your life, making it miserable. Get the surgery, and you may wake up with less pain than you have now. In a month, you should be having little pain and full range of motion. At two months, assuming no unrepairable soft tissue damage, you will have full use of the arm for a reasonable range of activity (no pitching baseballs or arm wrestling).
My wife had the surgery a couple of years ago, and wishes she knew about the procedure and had it done years earlier. Now, she rarely thinks about it. She's now looking forwardto getting total knee replacements.