They do have a separate chain. I think the chain is pretty durable, but you should change the spring and tensioner on it. Chances are it will be pretty worn. Mine (at only 248K) had the chain through the tensioner face and the spring arm worn more than halfway through Plus, I think you're looking at less than $10 for both.

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.