I have a save from ME1 and am using it for my first preview. My questions are:
can i use it for my second?
I heard playing as a female Shepard changes the stories. Is it possible to give my ME1 character a sex change in addition to all the other things I can change? Yes i went through this once, but I forgot all the options...lol

no you cannot sex change your import... 
yes you can use it again...
if you want, just make a femshep in 2 to see the differences

You can change class and appearance. That's it.

@sixghost said:

"You can change class and appearance. That's it. "

" no you cannot sex change your import...  yes you can use it again... if you want, just make a femshep in 2 to see the differences "