It can be restored. Does the cost matter to you? I would estimate the mechanical and interior restoration will cost around $20,000 not including any labor. That is doing it on the cheap using used parts and rebuilding/restoring what you have when you can. Sunroof parts are going to be almost impossible to find. Repairing the rust wont be too expensive as long as you do not have to buy body parts and complete panels, making your own patch panels, etc. A full paint job of good quality starts at $10,000 if you have it done.
Add it all up, then go look at the prices for a finished car, compare the time and cost between the two. You might find that you can buy a finished car for what you will have in this one, labor not included.
It used to be, we would say everything cost $100. Now, everything cost $500. Just a dash wiring harness for this car is now $700. Cluster restoration is $1000 if you have to send it off to be done.
In the end, restoring it yourself is a wonderful accomplishment, if the cost and time are not a factor.