What did the dealer say about code 114 transmission selector lever, that type of malfunction can cause a transmission shift complain? Try shifting the car manually and see if you have 5th gear. Did you spill any liquid on the shifter lever? The fifth gear problem is not valve body / solenoid related. Contact the dealer and ask them about that code. You had mentioned a radiator problem contaminating the transmission. Contact Mercedes, get them to pay for the repairs; they should be responsible; you might get a rebuilt. You should not just take things apart with out knowing the cause of the problem.