All 2007 Mercedes-Benz ML320 CDI questions

when i try to diagnose i got u0155 dtc .

i would like to know if its normal on 07 ml320 hard steering.

power steerig very hard.

I have all the parts, I have most problems with taking off the inside trim. There is a speaker in...

The car has 110,000 mile. I change the trans. fluid and filter every 50,000. At times (twice a we...