I assume you are going to wait until 2010 because your AGI is above the current limit for conversions ($100,000 and the limit goes away for 2010 and only 2010). If it isn't, you could convert half this year and half next year. The only other restriction to conversion is if you are married and file separately.
Any amount held in an IRA that is converted is not treated as capital gains, even if most of the amount is gains. The only taxation exception is if you had non-deductible contributions to your IRA.
IRS publication 590 discusses IRA's and Roth conversions and pertinent information regarding conversions are mentioned on pages 23, 40 & 64
http://www.irs.gov/pub/irs-pdf/p590.pdfHere's an HTML copy of 590 with a hyperlinked index page;
http://www.irs.gov/publications/p590/index.htmlIn short, the answer to your primary question is "no".
That's probably not the answer you were hoping for, but I hope that helps a little.