Another member i spoke to recently had similar worries as to making the right decisions. I find it easiest to break the project into groups and then make a list of "to do" jobs. Every strike through a job on the list is one less to do and then you'll make another list, then another until you're left with a "roadworthy list". It's just really hard to obtain the inspiration in the guts of a repair/ rebuild.
That's the part that sorts out the dreamers from the achievers. It's all the areas you don't see on a restoration, the ones that count, that can leave you with a with what appears to be an endless road. the rust may appear again even if you've done all your homework but when you get to that point you'll have the mental stamina required to do what needs to be done. That is the single largest skill i have learnt from restoring. The payoff is massive. 90% prep 10% finishing.