It does happen that blower motors work in high only before failing. I am giving you a walk through diagnsotic for your issue. If it says to get trouble codes pulled or to do any testing. Any Advance Auto or Auto Zone will do this for free and they loan out test kits.
So, use the link below to get to the diagnostic and go through it. You wikll have to back peddle to when the blower motor was tunning on only high to see why it failed and what got it there but the diagnostics are very helpful at process of elimination and really walk you through. So, follow the order in which it is written and let me know what you find.
Here is the link to get to the diagnostic;
Friday, November 9th, 2012 AT 2:13 AM