question members website monthly new content

Hi and Sorry for the rant below!
I have finally decided to come from the darkside of wysiwyg to WP as i see responsive websdesign is the future and i am getting to grips with the WP dashbaord/set up. My principle site I have been running for 4 years now is a member’s monthly newsletter (members password .hta access changed by me each month to get in – which i seen can be done easily all in WP).
At the mo I Upload each monthly website in its own months folder. Via an email each month I sent clients to a redirect page (that I alter the placeholder code) that will take them to the newest edition. Each months newsletter nav bar has the same main headings but different content and sub menus content but a separate nav bar link to get to previous editions list.
What is the best way to go about moving over as i dont want to start then to find i have been doing it wrong? (i realise there will be a lot of work doing the old pages in WP).
Obviously i don’t want the main nav bar to have a drop down menu with hundreds of children in the future. Sorry for numpty question but at the moment i cannot see how it all fits together posts Vs pages at the moment.
Due to the .hta access no one can see it unless they have the email links from me but I am happy for this to stay the same or for a new months ‘post’ blog page of content to appear on the web that I can add to each month and the new actual newsletter content and previous content to be reached via login only.
Any help will be most appreciated.
Scruffy.thedog