Guys there are two things going on here. First it sounds like you have the TEVES abs which has two circuits, a boost circuit (the Red Light) and the ABS circuit (Yellow Light).
If the boost circuit fails the red light will come on and the ABS system will detect the red light and turn off (yellow light on).
The most common failure at this age is the accumulator (black ball on top that spins like an oil filter) There are a sesries of tests at http://www.reatta.net/brakes/brakes_...eshooting.html
that you can run (all Reattas have ABS and if you think the GN crowd are fanatics...) and there is a very complete description in the 5E section of the service manual. Them is different.
Now there are two forms of "hard pedal". One is the conventional "no boost" and if you put both feet on the pedal you can get some stopping with the front brakes only (rears operate by magic. No boost, no magic.) The other is a very rare case where the main valve jams open and the pedal literally pushes back at you. 2200 psi worth if everything else is good. If this happens park the car until fixed. Period.
The best fix I know is a complete rebuilt unit (with new accumulator) from http://www.priorreman.com/
- about $600 and a lot cheaper than any dealer quote you will get.
BTW the TEVES ABS has its own computer module but I have never seen one fail, many people have spare good ones for a few bucks.
ps I am still looking for a factory CD radio for our 90 Bonne.