A defective alternator will always cause the battery to become flat quite quickly. (Although a flat battery does not necessarily mean a bad alternator). The "charging" light is a good clue to tell you the alternator is working providing it comes on with the ignition and gradually goes out as the engine speeds up.
If someone is advising you to replace your alternator to cure the Rev Counter & ABS light problem they are very probably taking advantage to make money for themselves or just guessing - or both.
A bad alternator will not cause the Rev counter to stop working & neither will it cause the ABS light to stay on.
In forty years of driving I have never needed a replacement alternator - don't change your alternator - change your mechanic.
Peccavi
January 2009