'07 Cooper S with timing chain noise

[bobzdar]

My wife's '07 S has recently started making a ton of timing chain noise, especially at idle. Over 3k rpms it quiets down and at anything above idle it kind of comes and goes but makes a racket at idle (sounds like a diesel). The tensioner was replaced at 15k under warranty as it made a slight noise that I pointed out when we took it in for it's scheduled service. Does it sound like the tensioner is going again? How difficult a DIY is this (I've rebuilt engines/transmissions ground up, so I can tackle pretty much anything, just need to know level of effort so I can plan garage time accordingly).

[Destro]

there is timing chain tension er that do go bad are cheap parts but can be a pia to change. If you know some one that has hands like the dude in the BK commercials call him the space is tight.

[bobzdar]

Well, they're replacing it under warranty as it was already replaced once when the car was new.