Gas tank question

[JoeKan]

My 72 burb has had an auxilary tank (1 gallon) that I've been using as I'm getting her fixed up. I think it's time to tie in the old tank and start using it. The PO had taken the nozzle off and had sealed the hole going into the tank. He was preparing to paint it when I bought it from him.
My question is "what kind of condition do you think the tank is in"? Do you think there may be condensation? rust? I don't think any dirt has gotten down in it because it has been sealed up. Is there a way I can check to see if there's anything in there other than taking the whole tank off? Or would I be better buying a new tank. That would be my last option as they run around $150.
Or maybe it's okay and I'm just nervous??? I've added a fuel filter to it so that should help.
Any advice would be appreciated.
Thank you,
Joe