Yep spot on, the rings should all rotate freely in their channels  

  I would always replace them.  You will be amazed how flexible and springy a brand new set is compared to a 10 year old, brittle, crumbly set. 
Glad you found a new cover!  £110 is a tad rich though.  I got one off ebay for £40 and threw it in the dishwasher, came up like new  
