Yep, blueprints not matching perfectly is a constant problem - no matter what you're modelling. Still, since we're not working in a CAD package, precise measurements don't matter too much, so just eyeball it - if it looks right, then it pobably is right
You've made a great start on that so far already. The only advice I can give you at the moment here is just to make sure that you've got each section right before moving on - and make sure to save (as different files) on a regular basis.