P/M acting up please help

[SlickTR]

Well to start off when I first got the car the brake light and pump stayed on way to long, never even shutting off sometimes, also would get a hard pedal every now and then. I ran the diagnostics and it led me to believe the pump needed to be replaced, after replacing the pump, things go a little better but still taking a bit too long for the brake light and pump to shut off leading me to believe the accumulator also needed replacing. I havent replaced the accum but the other day I pulled it out of the garage and all the sudden it had a really hard pedal and the pump was not coming on at all, never did this before. After removing and reinstalling the pump a second time it ran again but now wont shut off at all no matter how long it ran. At this point I noticed also that the passenger (pump) side of the resevior was not lowering. I disconnected the feed line coming out of the pump and the pump was pumping fluid, so it's working fine, but fluid was flowing back into the passenger side of the resevior through the back bottom hole of the resevior on the passenger side, would this mean the the master cylinder is shot and need replacing/rebuild? I need to know if it's the accum or the master cylinder, please give me and input you can....also where can I find the best price on a new master cylinder or a rebuild kit?