Help writing a USB driver

Hi all,

Any advice/pointers or instructions would be most helpful.  I am still
a newbie at embedded design so please humor me.

I have a datalogger module written using an Atmel 8051.  I want to add
a USB port to it so I can simply plug in a USB flash drive and have the
data automatically downloaded as a formatted text file.

I have read www.usb.org... but I still don't know where to start.  If
someone could point me to an online resource or a book... preferrably
something with similiar applications... that'd be great!

Here's a few of my questions.

1.  If I buy a USB controller such as those provided by Micrel or
Cypress... do I still need to write a "Host Controller Driver?"

2.  What parts of the USB protocol do I need to implement, and how much
of it is already implemented by the USB controller and the USB Flash
Drive.

3.  Do I really need to worry about all that protocol timing stuff ...
shouldn't the USB controller take care of that for me?

4.  Assuming that I get the answer to the three questions above, how do
I write a TEXT file to a USB flash drive?  I know how to do it if I was
writing a windows app... but this is different.  Anyone have any idea?

Thanks in advance.
Mercy