Hi NQ - welcome to what will be an exciting venture! I too am a newbie, and one of the best things that I have done is created a business plan before I did anything else. You can google search for business plan templates and find one that works. You may read a lot that you don't need one, or they are a waste of time. I firmly believe this is not true! I had a general idea of what I wanted to focus on, but then as I was writing my plan, the focus shifted slightly. The plan will help youfigure out where you want to go, and will help you get there. It is important to remeber that the plan is a living document, so it needs to be reviewed frequently (every 2 or 3 months at first).
As for getting your girlfriend involved, I would make sure that you have a solid agreement as to how things get divided out. Much like a pre-nup, you need a plan on what to do if the two of you ever go your separate ways. You can find many stories on the BP boards about partnerships that went south!
Keep active in your REI club - they can be great avenues to learn. Good luck to you!