Yard. first remove the pea gravel the best you can, when mowing it could become an expensive missle that will cause you more headaches. That should not be a problem. Secondly, builders are nortorious for hauling in the dirt that is full of weed seeds and other tubors that come up later on when weeds spring. Its too late this year, but next year before all the grass and weeds come up, get you a pre emergence weedkiller/fertilizer and that will solve many of your problems. As for now, I would just begin digging up those unsightly ones. Not knowing your region, the summer sun and heat will kill most later on. You need to just start out in the yard and keep the yard mowed, which is healthy for grass and plant those plants and flowers that will make things much better for you. Not too much you can do this year with weeds. OK.
Now, the flooring is another animal. You need to contact your builder if still around and discuss this with him/her. Since its so new and knowing that show homes do sell last, you should still have some recourse with them. Builders, at least some, are very hard characters to work with and the only way to get somethings done is to be very persistant and make noise. But first, be nice and professional and start the noise when nothing is getting done.
Secondly, document all visits, with builders, document all verbal conversations, document all problems, and have all this in writting. Hopefully you will not need to, but if so, and legal recourse is required, you will have some valuable ammunition.