Your description of the symptoms is not good enough to jump to the conclusion that the txb has gone u/s. The txb could be perfectly alright, power steering fluid doesn't get any closer to it than the accumulator.
Where exactly is the oil coming from? Near the water expansion tank or the accumulator?
There is a core plug at the back of the solenoid valve that can pop, dumping oil over the bulkhead faster than you can put it in. Only needs a replacement valve assembly from a scrappie.
Do not drive the car until this is sorted. If nothing else you could ruin the power steering.