Oh god I remember that thing. Modelling helper hasn't been around since 1.5. Good thing too, it absolutely sucked.
You should use this tutorial instead, it explains the process for what we use now:
www.minecraft-smp.de/e107_plugins/forum/..._viewtopic.php?30585
Just note that if you are setting up for 1.7.10, you need to type setupDevWorkspace rather than setupDecompWorkspace.
If that doesn't work for 1.7.10, do setupDecompWorkspace then setupDevWorkspace.
It'll make more sense when you read the tutorial