Included 6-26816 REA TrainSounds boxcars with each when I gave FARR 3 and 5 sets corresponding to the years of their births to daughter and son, respectively, to run around their Christmas trees. Both agree the sound effects are preferable to MPC-era chuffing and wailing, leaving the tethers disconnected and tucked in the cabs. May want to consider as an easy alternative, although the cost of obtaining one today may be equivalent to the price of an ERR kit.
Still endorse the recommendation to re-seat the tender electronics for the sake of preserving the original board, however inferior the sound effects may be considered.