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.
In Mass Effect, Sovereign, the Reaper that remained resident in the galaxy to montior biological life, was to have sent a signal to the Keepers on the Citadel to activate the Citadel relay and bring the rest of the Reapers back from beyond the edge of the galaxy. The Protheans modified the Keepers to ignore this signal, thus requiring Sovereign to have to assault the Citadel and dock with it in order to manually activate the relay. Shepard destroys Sovereign and buys some time for the Galaxy. My interpretation of these events was if Sovereign had been successful in activating the Citadel relay then the Reapers would have entered the galaxy at that point in time through that relay, destroying the seat of government and mopping up the galaxy from that point in space outwards.
Fast Forward to the very end of Mass Effect 2. A fleet of Reapers is seen heading towards the galaxy, under their own power. Rewind to Arrival; it is said that the Reapers will use the Alpha relay to spread throughout the galaxy. Doctor Kensen (was that her name?) mentions that with the destruction of the Alpha relay it would take the Reapers some months to couple years to reach the next relay. Since we know that all relays are interconnected it does not matter which relay they use really, but consider for a moment the location of the Alpha relay on the galaxy map. It is at the extreme end of one of the spiral arms, at the very edge of the galaxy. It is probably the relay closest to the Reapers who are moving towards the galaxy from outside.
To summarize: Protheans change Keepers and Sovereign fails to activate the Citadel relay; Shepard buys a little over two years time at the end of Mass Effect. Reapers "fly" to the galaxy from the outside (as seen at the end of Mass Effect 2). All mass effect relays are interconnected, so Reapers fly to nearest standard relay (such as the Alpha relay). Shepard destroys the Alpha relay, forcing the Reapers to fly to the next nearest relay. Shepard buys a little more time (a few months to a couple years) for the galaxy to prepare.
Best Answer
As Infiltrator you have to put 5 points into pistol before you can put points into snipers.
This is true for several Infiltrator talents. Namely:
Here is a link to the Infiltrator wiki if you have any further questions about how the skills work.