Hi everyone. This is my first visit to your site. I'm hoping to get some insight on whether this repair can be tackled myself. I own a 1987 420SEL with approx. 142K on it. While I was having my car serviced at the local Benz dealer, the shop manager suggested that the chain guides/rails should be replaced. He said that on high mileage engines such as the 420SEL and 560,these guides become worn and can cause the timing chain to jump,causing a major mechanical disaster. They quoted the replacement at around $1,000. Since then,I've put quite afew miles on the car without any trouble and she still runs well. I'd like to do this repair myself..just not too sure how involved it will get. Any suggestions would be greatly appreciated. Thanks!