Now that I have a few more minutes to type...
It is encouraging that there are so many new major appliances, and also that it looks like the owner actually bought RV specific items (its always a bad sign when the the refrigerator has been replaced with a cheap AC only dorm fridge).
It is discouraging that the owner didn't try a little harder with the Craigslist ad. The fact that there are no pictures, and very little information always makes me suspicious that they are hiding something.
You mentioned that most of the interior is "original." This usually scares me as well, as the more original a 40 year old trailer is, the more work you have to do to fix it up. I could easily imagine that someone bought a field-find trailer, and got a good deal on it, got it home to discover that most of the major appliances are shot, took the initial steps to replace those items, and eventually reached the conclusion that this rig still requires a lot of work and money to make it viable, so they are now just trying to cut their losses.
So just manage your expectations--this rig is likely to have frame and floor rot common to 70's vintage trailers, and will likely still require thousands of dollars and months/years of work to get it up to snuff. It is always dangerous to drive several hours to look at a trailer, because you can easily convince yourslef that the things you find are "easy fixes," and you end up hauling home much more of a project than you originally set out looking for.