Hello from Colorado: We are "up the hill" from you. Congratulations on your vintage
1967 Overlander 26. The body looks to be in good shape, very important. It looks like your is the "International" trim level which offers more special options in the trailer, like a TV antenna. The mid sixties Airstreams are very unique trailers, some say the best of the best of the vintage trailers. I am opinionated as I owned a 66 Trade Wind 24' and did a renovation to that trailer myself (see photo). I really enjoyed it.
You will find other vintage enthusiasts who would be interested in your project and willing to help and offer advice. Airstream Forums is a darn good website on all things Airstream. I suggest you start your "project thread" in the Airstream Knowledge Base, trailers, then the Overlander model, and then the model year. This category is found toward the bottom of the Forums page. Look for it there.
Read about other projects completed (or not) on your model. I might mention the 66,67,and 68 trailers were pretty similar in construction and parts. Any of those year's Overlanders would be similar to yours. The 1969 trailers started the new body style similar to mine. They are much different.
I now have a 75 Overlander 27' that I'm working on (see photos). Take a look at my project thread if you like. Generally, we just describe the "activity undertaken" such as cleaning out the interior, or removing the fridge, or cleaning the interior walls, or removing the axles, and always fun, removing the belly pan. Questions may by something like where do I get a new door lockset, or a new glass for the rear window, or what is the best converter. Others are likely to chime in and help out with some good advice for you to consider.
The Overlander is a great trailer, the right size for a family, but of course I'm opinionated.
David