Do you have a charger for it. If you do, charge the battery overnight then put it back in the gun and see if it turns on. Watch the screen and see if it lights up. That will also let you know what software it has.
You can get a replacement battery on AO for about $75. There is a guy who makes them, 1000mAh as apposed to the 650mAh that AGD makes/made. Somebody is also making new boards on AO.
You have a stock SS body, not a ULE body and are unsure of the battery and board. Those are the 2 things that will hurt you selling it. $400 might even be a stretch in the current market as the gun sits.