It's not much different than the form you get from the CD (1099-INT). Vanguard or whoever would send you a 1099-INT, 1099-DIV, 1099-B, These are for interest, dividends, and sales of stocks.
If you don't sell anything there will be very little tax consequence. You don't pay any tax on changes in value, you only pay on dividends, sales, interest, or sales within the fund itself. Nothing to worry about, go ahead and do it whenever you're ready and don't worry about the tax aspect.