Mercedes Timing Issues

I have a Mercedes E550 and got a p1200 code. The car started running rough and finally progressed to almost not running at all. I did some research and talked to the local Mercedes service manager and confirmed that my serial number of my car is one that has not had the timing gear upgrade. Therefore, I have to pull the engine. My question is: does anyone know exactly what parts I should change and who may have the best prices? The car has 152,000 miles. I will change the water pump, and all other bearings that the serpiteen belt runs on. Obviously the chain and the gear that is worn. I was wondering if the guides need to be replaced? I will change the cam magnetic sensors. Also read something about parts that should be changed on the camshaft itself ( don’t know the name)?

Thanks for any and all help.