I began my plunge into the ME universe around the first part of May this year. I began with ME2 and absolutely loved it. Then, I saw ME1 available on Games on Demand and bought it; started it that very night. It was pretty much a nightmare for me at first; the combat and squad controls were waaaay different, and don't even get me started on driving the Mako (you'll see). But, by the end of the game, I was already thinking about what class I'd like to try on the next run through on it. Started as an Infiltrator, because sniping from a distance is awesome.
I imported that character to ME2 and the experience was really different than what I had before; new side quests, people mentioning things I'd done in the first game, etc. I completed my second run through ME2 in only 10 days, playing about 4 hours a night. Now, I kinda miss that old Mako...
I've finally begun ME3 and yeah, I am already totally spoiled to the ending. I know what happens, but you know what? I'm like you; it's a game, life goes on, and I can always finalize things in my own head.
As far as any help I can offer, all I can say is dive into it, commit to your Shepard, talk to everyone after every major mission. In ME1, watch out for Krogans; they are tough if you aren't used to using yours and your squad mates powers efficiently. Watch what you say to Liara or you will find yourself in a romance with her...lol! Learn to love your Mako and take someone with tech powers with you when you have to use it. Inventory and upgrading your equipment can be a pain, but its worth it. Once you figure out all the crazy clunky stuff of ME1, the next game is a breeze comparativly. You'll find your way pretty easily, more than likely.
Anyway, welcome to the Mass Effect Galaxy!