How are the the rings removed/replaced?[/QUOTE]
To remove I use a pair of pliers or side cutters/ pincers go around the ring & turn it in on itself until it falls apart ,
To replace proper you will need a punch & die that matches the size as in the photo
if you buy a kit you sometimes get a set thrown in for free ,
Try a sail maker or decent chandler or even a tent or canvas cover supplier banner or sign maker .
I find its best to have another person hold something solid such as a lump or sledge hammer so you can then tap & swage with a smaller hammer holding the punch part until both parts go tight together .
If you can get hold of the eyelets but not the punch & die with a bit of care & gentle tapping & patience you can do it with just the ball part a ball pien hammer ,,, much easier with the correct size punch & die though .