What Relic1 said. You won't get better fuel economy unless you lower your compression and tune accordingly. Still then, it's a crapshoot. Fortunately you won't use that much more gas unless you just can't keep your foot out of it. Most people don't want to keep their foot out of it. I wouldn't. Not after all the work.

If you don't buy a turbo kit, installation will take as long as whatever you set yourself up for. I'd go with a kit unless you're replacing your internals.