You can pick up and play ME2 without playing ME1 at all. The gameplay is quite different and the game does a decent enough job of carrying the story forward whilst giving you the main gist of the first game. It's much lighter on RPG and heavier on action so is also easier to "pick up and play".
However, playing the first game will add a great deal to the experience. As you may know, many decisions you make in ME1 have an effect in ME2 and those decisions (as a whole) are uniquely yours. It's not just that the opening sequence is harder hitting but the little touches interspersed throughout the game. Without giving away any plot spoilers, you could meet or receive Emails from characters you helped in ME1, encounter a crewmate you romanced or simply have a character say "Hey I remember you from...!".
Here's a thought...you'll only ever get to play through both games for the first time once. Replays are fun but never like the first playthru where it's new and spontaneous. Play thru ME1 first, import your Shepard across and you will appreciate ME2 much more (and get a small starting Money & XP bonus). The galaxy will be shaped by you and it makes it more personal and better role playing. I actually quite envy you that you still have the opportunity to play them both for the first time. Have fun!
PS. Play Vanguard in ME2, Biotic Charge absolutely rocks :-D