Basically the same you do with an old car to get more money out of it. But also more work and you need to be a lot more patient, have more potential customers, idiots among them or people trying to beat down the price. Hard to estimate if it’s worth it. On the other hand it might be easier to get rid of the rest after you sold the most important stuff, kidneys etc. Maybe people are discouraged by having to buy the whole thing, but someone could be willing to get the rest for final evisceration.