C180 stuck in gear

[carlos_666]

hi there
im kinda new to this but here goes anyways

i bought a mercedes about 2 weeks ago, its a 1997 c180 espirit auto with 78k on the clock it was fine until about 2 days ago.i stopped at some lights when i moved off the gear would just not change even though the rev counter went up to the red line.so i bought some tranmission fluid from petrol and put about 1 litre into the car ( dont know if that was a good idea) but still same problem. so i took it to some automatic box specialist he connected some diag machine and he gave me this report i quote
"code 13-rpm sensor
code 103- intermittant rpm sensor
circuit board needs replacing"
and told me i need the conductor plate replaced (conductor plate,circuit board????? are they the same thing) he quoted me £450 parts + labour is that good or bad. and is this a serious problem. i could get the part for £110 of some parts dealer but i dont know how much the labour would be. is it hard to change this part.
sorry for writing up an essay.