DALLAS, Texas - The Big 12 Conference selected Tyrone Lewis of Oklahoma State as the Big 12 Wrestler of the Week for the period of Feb. 9-15, the league announced Monday.     Lewis led the nationally top ranked Cowboys to a 25-12 routing of No. 8 Lehigh last Sunday.  OSU is now 17-1 overall this season.     Against the Mountain Hawks, OSU won seven out of the 10 bouts, including Lewis' victory in the highly anticipated matchup at 165 pounds where he faced top-ranked Troy Letters in a rematch of last year's NCAA semifinal round.  No. 2 Lewis prevailed with an 8-5 win over Letters, to avenge the loss from the 2003 NCAA Championships.      With the win, Lewis improved to 28-0 on the year.     OSU ends its regular season Sunday with a 2 p.m. tilt against Minnesota in Stillwater, Okla.    2003-04 BIG 12 WRESTLERS OF THE MONTH / WEEK  November: Travis Paulson, Iowa State   December: Travis Pascoe, Nebraska   Jan. 12: Chris Pendleton, Oklahoma State   Jan. 20: Johny Hendricks, Oklahoma State   Jan. 27: Jacob Klein, Nebraska   Feb. 2: Nate Gallick, Iowa State   Feb. 9: Jake Rosholt, Oklahoma State   Feb. 16: Tyrone Lewis, Oklahoma State