IMO, you definitely want to import your Mass Effect 1 character into Mass Effect 2. All of the major choices that you made in Mass Effect 1 will be reflected.
For example, at one point you visit the council on the Citadel, and that plays out completely differently depending on whether or not the original council is still alive (same with the choice of who you nominated for the council, Anderson or Udina). The same goes for who you killed on Virmire (Ashley or Kaiden) and if Wrex is still alive.
The same is true for the side quests, to a lesser extent. However most of these only have the follow up in the form of an e-mail to your private terminal on the Normandy, but it's still cool to know that your choices had a lasting effect on the story.
If you had a love interest, it doesn't have a huge impact on Mass Effect 2. When you meet them, you share a brief kiss, but that's about it. You are free to have a new (different) love interest in Mass Effect 2, but apparently that will have some sort of impact in Mass Effect 3.
Bioware did an excellent job continuing the story you started in the first game. If you could make a choice in Mass Effect 1, it is reflected in Mass Effect 2.
As for importing characters, I'm not completely sure about this but I believe that you can import any play through for a given character (it's been a while since I imported my Mass Effect 1 characters). If you don't mind doing another Mass Effect 1 play through, I'd suggest starting again with your level 60 character (or whichever one you want to import), and make all of the decisions that you want to carry over to Mass Effect 2. You could always put the difficulty on easy to help things go faster.
If you want to know how a given quest affects Mass Effect 2, you can always check the Mass Effect Wiki.
If you don't import a Mass Effect 1 character, the game basically makes the big Mass Effect 1 choices for you. Also, some dialog that is present for an imported character is not present for a new character (mostly minor things, but some text wouldn't make sense if you didn't play the first game).
Finally, at the start of Mass Effect 2 you are able to change your class and physical appearance (don't worry, it makes sense in the context of the story). You can't change your sex or name, however.
It is possible but inadvisable to play Bring Down the Sky from the very beginning. While certainly doable (I've done it myself) you're probably going to end up reloading a dozen times or more over the course of the mission.
The Batarians are no pushoevers, and you've got the always "lovable" varren to deal with, who have a nasty tendency to sneak up behind you and eat you through shields. There is also the issue of one of the torch bunkers spawning rocket drones nigh-continuosly until you take out all the batarian engineers - and everyone knows what sorts of naughty things close-quarter rockets due to Shepard, shielded or not.
I would recommend a level of about 25-30 -- the goal is that you have enough abilities by that point to survive a little longer than you might otherwise. But, level alone isn't the best indicator of difficulty in this game; if you've already beaten the game once, you should have the VII spectre master weapons available as soon as you can afford them, and a good gun and good knowledge of cover will serve you better than the extra 100 health successive levels will give you.
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When I did this I prevented him from inspecting my ship. Other than that the only effects on the game is reputation, as described in your linked article.