I think there is a way to check for chain stretch. I think the $$$ to replace a chain and tensioner is aroun 800-1000 dollars US, from what others have posted. I have the same year and model as you. My mechanic said as preventative matenance it would be a good idea to replace the chain rails (or guides). I guess the biggest problems aren't with chains breaking, but with a rail breaking loose. This causes the chain to skip some of the teeth on the gear or else the rails get caught in the chain and cause major damage. Other than that get some kind of rust proofing done and you should be fine.