Keep an eye with the setup see if it loses time too quickly like a few minutes or more per day. I would appreciate a picture of the underside of the board. Oh, you can buy some solder wick to help with desoldering pins. Drove me nuts trying to unsolder a row of pins before I knew solder wick or desoldering iron.
Eric,10 minutes a day is a bit too much. Are you keeping the shield in doors with constant temperature? The time can only be accurate with DS1307 if the crystal is kept at constant in door temperature. The crystal oscillation frequency is a function of temperature.