I am currently working on H1B status which expires on September 28th 2010. I want to go back to school for a PhD and have applied and been admitted into a university. (I am not getting fired and the company is doing well.) The classes begin during August 2010. What I would like to know is

1) Who files for the change of status from H1B to F1? Would the school (International Office) do that for me or do I have to find a lawyer to do this myself?

2) Either way, what amount of time before my H1-B expires should I start this COS process to avoid problems like COS not coming through before my H1B expires?

3) If COS doesn't come through before my H1B expires, would I absolutely have to return to my home country OR can I wait here in the US until the change is approved?

Thanks!