Paul,
Yes, you're on the right track. Depending on your age and the life annuity payout options you choose, you could use a portion of your 401k balance to buy a life annuity to close that $2,000 a month shortfall. The remainder of the account could be invested for long term growth to provide you with an inflation hedge.
Before you do this, however, you should also factor future Social Security benefits into the equation. Recently, the Social Security Administrations website, www.ssa.gov, introduced a new benefits calculator that will automatically load your earnings record and project your future benefit. Given your 401(k) accumulation, I think its a good bet that your combined SS benefits will be over $2,000 a month.
If you are retiring early, either at age 62 or before, the thing to do is use a portion of your 401(k) assets to "bridge" the income gap between the day your salary stops and the day your Social Security benefits begin. While you may be tempted to take benefits early because it will reduce what you withdraw from your 401(k) assets, you and your spouse will be better off if you delay at least your benefits, allowing them to grow. Then take your benefits around age 68 or 69.
The benefits of doing this are covered in detail in my new book with economist Larry Kotlikoff, "Spend 'til the End" (Simon & Schuster, June 2008). The subject is also covered in a number of columns on our AssetBuilder website.
Here is one of those links. Links to other columns on this topic can be found at the bottom of the page:
http://assetbuilder.com/blogs/scott_burns/archive/2007/10/31/yes-for-many-it-s-better-to-take-social-security-benefits-later.aspx
Scott