There is a tutorial. If you've used Stardock yet, you'll see that you can download tutorial videos. Those are decent.
And go to the Databanks link on this very galciv2 site, on the top left corner of the pages, just under HOME.
Also, read faqs, which exist for this game.
Also, read the manual that I'm sure you got with the game. It's probably .pdf format in the same directory as GalCiv2.
Also, search this site for basic strategy guides.
The reason there's nothing by the devs about what you should build first, is that it depends entirely upon your strategy. So, you can do research as I've proposed, or you can learn by trial and error (as I myself did). Start at lower settings, try to get up to normal/tough/challenging, and you'll find that you can get the hang of it in just a couple of games. At least the basics.
3) after reaseching a weapons/ armor upgrade, do my ships that have already been produced automatically get that upgrade, or do have to manually select and upgrade them? what about new ships that i produce?
For this, you need to go to Starport, and design new or upgraded ships. I'd start with a new ship, picking your hull size (looking at hitpoints, size, and cost), then putting what you want on the ship. Then name it something unique. Then choose to build that ship in a planet's starport. Your ships won't automatically integrate what you research. You have to do that by designing it. The look of the ship is irrelevant to how it performs, by the way.
Good luck!