if your old bike had quality parts on it and they aren't broken, I'd stick with them and not try and convert it to the latest bazillion-gear fad.

personally, I don't like more than 9-speeds, I think the current trend to 10 and 11 speed cassettes is silly and insane, except maybe on tour-d-france racers. a 2x9 or 3x9 gives you way plenty of gears. quite likely, your old dusty bike just needs cleaning up, new cables, some grease (wheels, headset, bottom bracket, if not sealed cartridge type), and maybe a new chain. worse case, a new freewheel or cassette. the rest is probably in fine shape if it wasn't damaged when you parked it. ok, new tires. there's some awesome new tires available, like Vittoria Randonneur Hyper, Continental Gatorskin, etc.

re: manuals/howtos, two great sources are the how-to sections on the Park Tools webpile, and Sheldon Brown's webpile.