Greetings Newtothis73!
Welcome to the Forums and the world of Vintage Argosy ownership!
When you are looking for a repair/service manual, you will be looking for an Airstream manual as it doesn't appear that there was a separate Argosy service manual. You will find that there are Argosy specific owners manuals, and they are offered from time to time on E-Bay.
One thing that I would suggest is to look for a three-piece rock guard for your Argosy's front windows. While those deep-wrap side windows can be replaced should one be broken, the replacements will be solar gray tinted and quite expensive -- one broken wing window would more than pay for the rock guard.
Good luck with your coach -- Vintage Argosy/Airstream with a Vintage tow vehicle -- the only way to go . . . . . . .
Kevin
1975 Cadillac Eldorado with 1978 Argosy Minuet 6.0 Metre
1975 Cadillac Eldorado with
1964 Airstream Overlander Land Yacht International