Hello , I have a 98 w210 e 300 d. Mercedes.  Problem started with coolant in the transmision. Took it to my mechanic he said oil cooler. Put new cooler changed filter and fluid.  drove it 125 miles on shakedown test, drove through automatic car wash put in in gear car would not move, no forward no reverse. Shut it off, and it would move maybe 100 ft, and quit moving.  Fluid level good. check engine light is on . Generic o.b.d. says engine electronics. Should I start by changing the valve body? Car has 150 k. Thanks.