Okay, let's tackle your questions one by one. The advice you've been given by two repairers doesn't really gel. For a start, you have a mechanic telling you it's an electrical problem, and an electrician telling you it's a mechanical problem. Sounds like neither of them know what's up here. There's a big difference between an engine that has no spark and an engine that needs a complete rebuild, in both dollar and effort terms, so you need to get an independent assessment of what's really wrong with the thing and go from there. If, for instance, it's a simple case of needing new spark plugs or coils, then it's worth fixing. If the engine is indeed toast, then a new one is probably going to cost more than the value of the entire car.
Which brings us to your second question. Given that a 1998 Forester is probably a $3000 to $5000 car in good working order, you're not sitting on a gold-mine. While you could potentially make more by wrecking the car and selling it in pieces, you have the hassle of physically separating the car and selling it piece by piece with cleaning, packaging and mailing the parts one by one. Then there's the fielding of hundreds of emails and phone calls, not to mention the hassle of having a dead car in your driveway for as long as it takes to sell all the bits. Even then, you'll eventually have to have the carcass taken away. The alternative is to sell the car to a wrecking yard to handle that side of things, but you'll be lucky to be offered more than a few hundred dollars to have the car picked up and removed.
The option, to answer your third question, would be to have the car electronically scanned, find out precisely what's wrong with it and make an informed decision from there. If the thing is fixable, great. But if it needs a new engine, it might be time to think about a replacement car as spending thousands on a 25-year-old car that will certainly be showing wear in other areas, doesn't really stack up.