1. I believe that there is a function called .CurrentTime which returns a TimeSpan variable. I think you can use it to get the current time.
2. Im not too sure but maybe you can make calculations based on the time you want to seek and convert it into Position? I think there is an example in NAudioDemo where you can seek where to play the file.
Goodluck! Also, may I ask how you are playing the file? Do you know of any other way to play a file rather than using the IWavePlayer? Im having trouble because I need to play a file while controlling the # of bytes that are read each time.