More facts would be helpful. You can reply to your first post to add the details or edit your post. Just from your subject line there's not a lot I can tell you except this: the fact that it was "obvious" the gun had not been touched in a long time isn't all that helpful to you. Federal law and likely Nebraska law too prohibits felons from possessing a firearm. If you know the gun is there and have access to it that's generally good enough to be considered to be in possession of it. So a gun in your home, even if you hadn't touched it for a long time is still in your possession if you knew it was there because have access to the gun and can exercise control over it. The whole idea here is that felons aren't supposed to have access to firearms. If you are charged with possession of that firearm then, as quincy says, you really need a criminal defense attorney.
If the police found a Browning Model 1922 that was rusted so badly that the slide wouldn't move stuffed in the bottom of an old chest marked "Sgt. Bill Smith, 1944", then you probably would be ok. If the police found a Glock 22 on the top shelf of the towel closet with not even a light coating of dust, then you're probably not going to be ok. Either way, the police could "take you in" for it.
Nebraska “explicitly and unequivocally prohibits a felon from being in possession of a firearm” and “possessing a firearm includes purchase and possession of antique firearm” and the doctrine of constructive possession applies.