Reprogramming oko-lavamat 74335?

My 6 year old AEG oko-lavamat 74335 is playing up a bit by not allowing "quick wash option" on 50 deg. setting (light doesn't go on) and always stopping at "Pause" on 60 degree setting, requiring the button to be pressed again to finish the wash. Suspect it's a control computer problem - any way to fix this short of calling in the (expensive) cavalry? Is fitting a new unit something a reasonably technical bloke can do himself?