Hi guys,
First of all, thank you for your support,
My question might have been answered in somewhere else but I didn't find exactly what I needed to know, so I'd appreciate if you guys help me out about this:

(I am a non-resident student on F1 visa and we don't have tax treaty with US),
What happened is, last year for 2007, I filed the wrong form 1040 instead of 1040NR,
(this is the first time I filed tax)
So I got refund around 800$ which I shouldn't have plus I received a stimulus package of 300$.
I found out the mistake this year,so I want to amend it, I am also filing the right form 1040NR for this year 2008,
So, my questions are:
So far, what I found out is that I should file the correct form 1040NR+8843 for 2007 plus 1040X and send it to IRS, but I still have following questions:
When I fill out the correct form I found out that I should have gotton 400 instead of 800, so that means I got 400$ extra from them.
1. Do I send that 400$ back to them with the amended form or Do I send the 1040X only first and wait for their reply? How is the payment made?
2. What about the stimulus package, 300$?where do I send it back and when?
3. what about penalties and interest? Is there a waivent thing for them?
4. I also read If I send the amendment form 1040x before this April 15 I don't have to pay penalty or interest, is it true?or how do I know how much more I should pay them?

5. Also, what about state tax, do they have also amendment or penalty, do I send the same 1040X to them?I also have to pay them some money to them, what should I do?

If someone could guide me to the right procedure, that would be amazing,
thank you all.
Regards

1) Either way.

2) Send it back as a separate check.

3) You can ask to have the penalties waived, but NOT the interest.

4) False; that was if you amended the return before 15 April 2007.

5) The state probably does NOT need to be amended, as the state does not care about your international student status.