ive RMAed several msi mobo's... its very easy
just download the .pdf rma request sheet
fill in the blanks and email it back to the provided email address (you need acrobat, not just acrobat reader) or you can fax it in
then 2 days later you should get an email saying the RMA was approved
you dont need any kind of reciept or anything like that, it just goes by the serial# on the board, and they have 3 yrs