The ring is bolted to the spider/crank arm via (usually) 5 bolts. The diameter of the circle these bolts are positioned with is called the "bolt pattern" (think lug bolt circle if it was a car wheel). You need to know this dimension as well as the number of ring bolts. I suspect you'll have a 130mm bolt pattern with 5 bolts as that's a very common spec.


Once you know this spec you can search for any other ring that matches that spec AND has the same tooth width (as in 8 or 9 or 10 speeds or 1/8" width, whichever your drivetrain has). In theory any one brands of ring that matches all the specs will interchange with your brand crankset. There are exceptions though. This is why those who don't know how to figure this all out are often better served by working with a LBS to source and maybe mount the new ring.


Which leads me to further comments. Why were you unable to use a der. to shift after installing the "warranty" ring a year (?) ago. Why didn't you get help then from a shop or other experienced person? This problem might have been a small adjustment to fix. That you were unwilling to get that problem fixed I find interesting...


As to chain/cog/ring wear rates- Yes a ring can wear out in a year of use. You don't say how many miles/K's you ride, whether you are an all weather rider, whether the roads you ride on are gritty/salty/muddy, whether you care for the drive train by cleaning it periodically, whether you lube things, whether you tend to ride on one ring a lot (and having to shift by hand certainly supports this possibility). How quickly a bike wears has far less to do with age and far more to do with the use conditions and cycles of use.


I have at times suggested much what the shop has. Replace all the wear items to re base line the drivetrain with good parts well installed and well adjusted. Generally piecemeal replacement of parts that are installed by inexperienced people and not well adjusted results in less then usual life spans and sometimes results in other problems. Andy.