The Air forums is a great place to learn all things Airstream! The search function often gives more information that one might like... but if you have specific questions, just post away and many of the good folks here will respond!
You might take a look at this link on price vs. condition for Airstreams. It doesn't go up to 1983, but reading through the information might give you food for thought. Price vs. Condition - Airstream Values
You could also look through the members list and find others with a 1983 Excella and post a question to them if you have specifics.
A great way to learn more about Airstreams is to attend a rally near you. (It is winter and might not be a lot going on, but many times you will find Airstreamers out camping when others stay home! A rally can provide you with lots of insight. You can meet other Airstreamers, see their trailers and "talk trailer" all day long...
This is a great group and there are even folks who will do inspections of potential purchases for you (many for free, or just for gas to get there). So, ask away....
Welcome to the forums! I might add, retirement is the best thing we ever did!