Looks like a really nice unit. Unfortunately the only way to really determine it's value is to place it on Ebay. I assume you are wanting to get as much for it as possible and that you'd like to sell it as soon as possible. With that said...it's really only worth what someone is actually willing to pull out of their pocket and hand you for the unit. Don't get me wrong I'm not a big supporter of Ebay either.
To have a unit restored cosmetically and just freshened up internally (assuming you had a good working unit) will run you at least $150.00. Add the price of a good core (about $150.00) and it should easily bring about $300.00 but you'll be hard pressed to get it. I have a box full of 8 track players in that same condition and I usually list them (not on Ebay) for $150.00 and of course then the "Will you take $50.00" offers start. Honestly your unit would probably cost $300.00 to replace but you have to ask yourself would I take less and how long do I want to sit on this thing and hatch it?
Good luck with your sale. You better move it before they repop it or you wont be able to give it away.