Sup Yoga.
The average playtime for your first Fallout game can take anywhere from 15-25 hours, so I'd estimate about a week at the most for you to beat the game.
You can buy and download the game at GOG for 5.99$ (US)
http://www.gog.com/en/gamecard/fallout/
GOG sells internationally so you can buy it no matter where you live.
As for a walkthrough, Per's guide is the absolute best, it also has the info about builds and stuff you need to make it through tough patches and to get the most out of the game.
http://user.tninet.se/~jyg699a/fallout.html
I really suggest you go through it blind the first time though, it's a very interesting and memorable game to experience fresh.
As for the version, downloading the latest patch (which comes with GOG's download) and Killap's fix patch is the best course of action. Any High Resolution mods are ancillary and shouldn't really be necessary, the game isn't pretty, but it isn't terribly ugly either and gets the job done.
I wish you the best of luck and am looking forward to your updates.