Welcome....
Here's a manual for it ...that should get you started.
http://media.browning.com/pdf/om/auto5_light_om_s.pdf
If you have some buddies that are into older shotguns / the Auto 5's are going back into production - but its a different mechanical system than they had back in the day - but some of your buddies may give you a hand with it.
If you don't know anyone that is familar with the Auto 5's -- I'd find a gunsmith that is knowledgeable on them ...have him or her - go thru it / check it out - show you how to clean and lube it properly - or they tend to be a "jam O-Matic" ...if you don't know how to take care of them. But properly cared for ...they're still solid shotguns.
You can also go to the Browning website ...and date your gun.
http://www.browning.com/customerserv...index.asp?bg=x
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If you do some searches on the forum ...there is a lot of stuff out there / discussions on the Auto 5's.