Sandy - you just described ME! Well, except #4 - it's my job, so I can't claim to be totally ignorant.
When I can find sheet music, I use Noteworthy Composer to enter it note by note, counting the bloody lines....then save as a midi file (you don't need a midi input device to save or download OR convert a midi file) and then use alan's software to create the stuff for posting. [This is the way I find out what stuff sounds like from the Levy sheet Music site]
Or you can SCAN it, and send Dick the file that results.
Or you can blackmail a friend or relative who reads music into transcribing it. the last method does not work very well.
I REALLY wish there were some talented person out there who would accept cassettes and transcribe them. I have a bunch of songs I'd love to be able to transmit. Of course then I would actually have to record them.