The "grinding" sound leads me to believe that your clutch is not completely disengaging. Does it also do it in Reverse? First gear and reverse gear is not syncronized. Sometimes it helps to go to reverse, then bring it back to first to keep from having to force the thing into gear. Forcing it will bend the shifting fork inside the transmission. If it has been forced a few times, you may allready have a bent fork. Anyway, if it is also "grinding" going into Reverse, it is time for a clutch.