since you're asking for opinions, here's mine, worth as much as you paid for it, too..
anyhow, currently, in the state it is in at this point with the rust and tired interior you'd be hard pressed to get more than $2500 out of a knowledgeable buyer. i, too have a special affinity for the early VINs (i have 2760403 & 2760440, both rust buckets and colorado). fortunately, i actually enjoy the process of rust repair. if you are paying for this work you will spend a small fortune. you will likely never recover your cost. the market is just not there.
so, in my mind, you have two choices, lower your expectations and embrace a driver-quality car and spend accordingly, or cut your losses now and look for a better starting point.
your best chance at maintaining value is to keep it as close to 100% stock as possible. you can change rims and suspension but keep the rest stock.