Will running distance make me a slower sprinter?

Depends on volume: If you are well trained (running 2 years plus), and truly sprint specialized (distances 400 m and below) then running distances (say 5 miles or greater) will probably slow you down. This is because 1) distance running can to some degree train fast twitch fibers to act more like slow twitch fibers, and 2) distance running will take from training volume that could otherwise be used for speedwork.