You cant tell which chain has went until someone has had the cover off. Its not too hard of a job just hard to get to and fiddly. I paid a friend of a friend £130 to fit, £170 for timing and balance chain kit from ebay (look up company called trenchii on ebay) timing chain kit did not come with the small sprockets so needed to buy 1 from saab as Vauxhall up here didn't stock them so another £45 that. Oil and filter £30. So £375 all in mate, pleased its done now everything running perfect.
Hope this helps