You can set whether its stereo or mono. You access the buffers of either channel, or a mix of them, by bufferSize() and using left.get() , right.get(), or mix.get() respectively. See the getLineIn example.
Your current millisecond of the 'playhead' can be gotten by the position() method, and the total length by the - you guessed it - length() method.
There is a boolean isPlaying() that will return true or false depending upon, well, whether the sample is done or not.
This is assuming that the sample is not set to loop.