It's pretty old. 8 years is a long time for a computer! I ran it through www.gadgetvalue.com with the provided specs and it says "Price range: $133 to $138".
And if you do sell it, make sure to wipe the drive as @MinecraftModsINFO had said. It's very important that you either destroy or wipe the drive several times, or whoever you sell it to can possibly access all of your documents and pictures, website logins, browser history, chat logs, game logins, etc.