Timing chain on a M119 is definitely a job best left to a pro MBZ tech. Factory literature clearly states that this is not a do it yourself job. My 92 M119 has 205K on original chain. Chain stretch should not be worried about until it starts making the noise from the tensioner not being able to compensate for stretch anymore. Ignition components are critical to maintain. Also use a high quality lubricant such as Mobil 1 15W 50 with a factory O.E. filter. These engines tend to run a little warm and need all the protection they can get. Don't be concerned with the 106K miles, That is still low mileage for an M119. Also, do not neglect the cooling system. Make sure and drain both sides of the block along with the radiator. USE FACTORY APPROVED FLUIDS ONLY. There is a good reason for this.