I'm an international student from Morocco and I made a mistake while filing for my taxes. I'm on an F1 Visa and I should have used 1040NR instead of turbo tax. I already got my tax return which was about 400 and it's a lot more than what I would have gotten using 1040NR. I sent everything on time and also filed separately form 843 and 8316 to get my SS and Medicare withhold by my employer (on campus student employment).

As I've been reading, I think I will have to file form 1040X along with 1040NR. But the problem is the extra money that I got from IRS. Should I write a check containing the exact amount I got from IRS or only refund the difference ? Can I write an email and enclose it with the two forms ? Should I refile forms 8316 and 843 again to get my SS and Medicare back ?

File amended tax return Form 1040X with properly done nonresident tax return and form 8843.
Wait for 4 months and them file Form 843 with required documents. http://taxipay.blogspot.com/2008/03/non-resident-exempt-individual-social.html