I love your attitude – if I had any power at all for hiring I would fly you in for an interview for sure. That said, I have no power to do so. Where are you looking for positions? I know you posted on this earlier, but perhaps you can give an update?
Your ribs could fill, it depends on how tall and thin they are – if they are much more than a few wall thickness in height then you could run into trouble. Basically it comes down to the ability of the material to flow through the mold. Long thin sections can be difficult to fill as the material flow is impeded by a combination of factors (material cooling, inadequate mold pressure, material viscosity). Fins are added to heat exchangers to increase their efficiency and tall thin ribs are pretty much fins that allow/force your molten material to cool, potentially in ways you do not want that lead to voids, warping, and internal stresses.
For plastics, there are lot of free resources online. One of my favorites is the Proto Labs cube. It is a free molded part that shows a lot good practices for injection molded parts. It is also great as a fast reference for different approaches to common features and for some simple textures.
Proto Labs also has a decent online resources section
http://www.protomold.com/Resources.aspx
Bayer Materials, DuPont, Sabic, and other material manufacturers provide fairly comprehensive design guides for free, as well. The Bayer guides are very good, here is a link to their resource center (you will need to register):
http://www.bayermaterialsciencenafta.com/resources/index.cfm?f=10247629-D94D-FDDD-B63BB6BDC92B451A
If you don’t want to register, you can find the guides hosted other places online. Here is the plastic part design guide that was uploaded by someone at RIT.