your best bet is probably to sell it on eBay. I'm guessing you'll get somewhere between $500-1k for it. Depending on how much effort you are willing to put into it... the low effort route would be a no reserve auction with a low starting price, like $99. A higher effort route would be to start with a reserve like $500, and if no one bites on it, auction off the pieces with no reserve and low starting bids. I would sell the vise, collet set, and any other tooling all in separate auctions, and then break down the mill into X,Y,Z table, motors & flashcut controller, spindle, and motor & speed controller all in separate auctions.
In good condition, Sherline stuff will average about 2/3 of list price (their website lists it all), but some will go higher and some will go lower, especially stuff with rust on it. Lots of people watch eBay for Sherline stuff, especially the stuff that isn't listed by professional re-sellers. Good luck.