Stocks Set to Open Up as Oil Prices Fall  NEW YORK (Reuters) - Stocks were set to open higher on  Tuesday after a long holiday weekend, with U.S. oil prices  falling more than a dollar and Seagate Technology &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=STX.N target=/stocks/quickinfo/fullquote"&gt;STX.N&lt;/A&gt;, a  computer hard-drive maker, raising its first-quarter profit  forecast.