1) Yes, though it's pretty rare.
2) You can get information about them by interrogating prisoners. Stapler, realistically, only from Guild Team leader (other enemies are much rarer), Wrench is a dirt common unlock from labourers, tough civilians and highwaymen.
3) Aw man, it was your saviour, treasure it, build a hideout for it, with angar in the middle and sacrifice slaves for the glory of the Airbus.
Jokes aside, airspeeder and aircar have less hands on deck (3 and 4 vs 6), so it would be harder to do missions. There would be a story mission in midgame where airbus is the strongest option, so you definitely don't want to sell it. Good upgrade over airbus would be shadowtech ships you get after unlocking your codex. Expedition is a horrible substitute.