Hi!
It's really great that such 'repairing' sites exist. Also the 3D print platform Thingiverse is connected with Make Printable I think so I tried it once.
With big objects, it worked quite well because the changes are not too big.
But when I tried it with my Lego Minifigure, the hands suddenly seemed like those of Hulk because they were 'too small'! So just modelling and repairing is way not enough, it's better do design your model with the fact in mind that it should be 3D printable.
Regards,
Christoph