Of course you can. But it's not easy. It's only been done a couple of dozen times, much less really because most amendments were not a "repeal" but rather an addition. One of the "repeals" was not of the original Constitution, but of a ill considered amendment. (21st and 18th amendments). The 17th amendment as well as the 12th and 20th were definitely repeals and/or modifications of parts of the original Constitution.
You can only amend the Constitution to repeal the Constitution, you cannot just “delete” parts out as Sara proposed.
http://www.usconstitution.net/constfaq_a7.html
The repeal of any part of the Constitution requires an amendment to the Constitution - this includes the repeal of a previously passed amendment. So, the process is well defined in the Constitution, and is detailed on the Amendment Page. In reading that page, you can see that you were almost right - the biggest mistake you made is that the President is not involved in the amendment process in any way.