New Tax Codes and Stock

Calvin, a client of yours since you opened your practice, has over the past few years become very intrigued with investing in the stock market. He has interest bearing securities and dividend paying stocks. He also owns U.S. Securities. He is considering selling $400,000 in stocks.  He doesnt know if he should sell additional stock for a loss to help offset the stock sale of $400,000. Calvin called you to ask what tax consequences the interest and dividends will have along with the stock sale. What tax advice would you offer to Calvin in planning for this situation?