Graphics.DrawImage will let you do this:
public void updateWithSprite(int x, int y, Sprite sprite)
{
Bitmap sprBitmap = sprite.getBitmap();
Graphics g = Graphics.FromImage(this.bitmap);
g.DrawImage(sprBitmap, x, y, sprBitmap.Width, sprBitmap.Height);
g.Dispose();
}
See also: http://msdn.microsoft.com/en-us/library/aa457087.aspx