Greetings, Nancy! And Congratulations!
Although there was no Owners Manual in 1958
, there were brochures and sales literature which may be of interest. Some of these are available online at the VAC site.
Check out www.airstream.net/members/documents/index.html
The '58 is not represented, but the surrounding years may be useful.
Also, the VAC publishes a quarterly magazine called the Vintage Advantage. The current issue has a comprehensive article about the Airstreams of the early 50's. I believe that the next issue will focus on the late 50's, so you might look for that.
Finally, there will be a VAC Vintage Rally in your neck of the woods (Duncans Mills-Russian River) in early October. Although the rally is filled, you might be interested in the open house on saturday, Oct 11.
In any case, Welcome, and smooth sailing!