Can't hurt to go in with a base of knowledge when talking to a lawyer.
There are plenty of people on HN who have had experience here and I think we're all smart enough to sort out the speculative responses from the responses that look like: "At my company (x43.com), we just went thru this and here is what I learned:"
Seriously: you're being offered a lot of free advice, some of which may potentially cause you significant problems down the road.
If you're serious about developing a product, you're going to need a lawyer at some point-- and it sounds like you've just reached that point.