How long is the lecture? You're in for a lot of typing. I h8 transcribing! I found a cool site once that let me speak into the mic and it did a fantastic job recognizing exactly what I was saying. I couldn't figure out how to have it transcribe the original audio- that would have been too easy!
I used to transcribe IEP meetings from home and got $1.50 for every meeting minute transcribed. Definitely worth the time with that whole mic discovery.