The incomplete information is there for two reasons:
1) Nobody knows? Nobody can be GOD of anything
2) Trial and error is encouraged to gain knowledge, then once you've gained this knowledge, you're in a position to teach. Now, you may be wrong, sure, but finding a good teacher is RP in and of itself. Trust me, there are characters who are good at sneaking, certainly better than your character early on, so they've figured it out and may very well be willing to teach the right chummer. For a price.
The good news is that if you put stats into intelligence, it's still good. No stat is without its uses, so try not to sweat it too much like Froggy said and let the RP guide you.
Final final answer? If you REALLY feel like you missed the boat on a build, you can do a 1-time respec later in the characters life to fix that.
Hope this helps :)