I want to know how much it would cost for a new ECU as I think that I've been over quoted for the work.

We dont' have any info for these cars. A good pro type computer can tell you what is wrong with teh abs or send you in the right direction, the type in auto parts stores normally can't read abs codes. If your abs isn't working you will still have brakes just not with abs. Also check your battery if it's old or not giving good voltage it will cause computer screw ups.