Welcome to the forums and congratulations on the purchase of a great trailer. I was on the lookout for one of those for years -- it's the year I was born.
Belegedhel gave you good advice. Don't take apart panels that were bucked together. They were assembled outside. In fact, everything in your trailer came through the door for assembly. You should be able to easily see which panels were put on last, since they overlap the previous panel.
I STRONGLY recommend filming everything before you take it apart. Narrate your film with your observations and closeups. I've found the hard way that pictures don't capture everything and that sometimes a zoom in on a quick film has saved me a lot of time.
You'll see as you take apart panels that there are hidden rivets. Circle or mark these for reassembly. Otherwise you may find yourself installing, removing, then reinstalling rivets again.
There are a number of threads on this forum that go through the entire process. I highly recommend studying them before starting, or at least the ones closest in age to your trailer. There are many tips that will save you hours.
Here's a link to get you started: click here