If your booster is shot there is a easy test to determine this. Press the brake pedal (WITH THE CAR OFF) when you get maxium travel hold the pedal at that postion. Then turn the car on if the brake pedal travles farther down towards the floor then it is not your brake booster, if it does not then it is your brake booster. Most likely its not tough. What problly happened is whoever was pumping the brake pedal ,if you were bleeding by foot, pressed on the pedal to hard ( you should never allow the brake pedal to go all the way to floor) and messed up the muffler/bushing inside the master clynder itself causing the hard pedal you are describing. Ive seen this problem alot, (im certified in brakes) and people bust that bushing all the time.