Can one get a copy of his tax returns of a given year from the IRS?<br/>How long does it take?<br/>And how much does it cost?

you cannot get a copy of someone else's tax return. If you filed married filing jointly (so you are on the return too) you can get a transcript for free for the last 3 years. A copy of the actual return is $57. Have a look here how to obtain a transcript or a copy:
http://www.irs.gov/newsroom/article/0, id=105370,00.html

Actually, transcripts can be sent from the IRS all the way back to 2003 at NO charge to you.