whoever told you that chains dont ever need to be replaced should be shot in the arse with rocksalt. just look at any number of 2nd gen trucks, mine included after only 32000 miles. i know thats a different situation but still. anyway, if it is indeed a belt i would go ahead and have it swapped out. but 750 bucks sounds like alot of cash. are you not mechanically inclined? it should be a fairly easy job. more time consuming than anything. if its a chain, wouldnt hurt to get it looked at i suppose.