Having owned most of the levels of most of the main component manufacturers, all of the components work just fine, even the low end stuff. My first road bike was an aluminum cyclocross bike with shimano sora and 2200 (bottom end) and it lasted 2 years and several thousand miles of traveling before I sold the stuff off to try a different style of shifting. The components lasted longer than the 2 frames that I broke while the parts were on it including 2 winters of riding. Point being, you don't need to spend a crap load of money to ride road, especially if you don't think you'll be doing thousands of miles of riding which is about the only time you'll start noticing if the higher end components last longer. Shimano tiagra works well and so does shimano sora.
Needing to start with 105 or better is for the birds, in my opinion. It only applies if you plan to race and/or get hardcore about road riding. Filling in mtb rides with a road ride doesn't give the impression that you'll be doing 50 mile road rides several times a week. I raced with shimano sora with thumb shifters my first year of cyclocross and no one I beat knew I was riding low end but me.
Don't worry about grams, it just costs money to be lighter and if you're not racing it's not that big of a deal. Best advice is to get a cheaper bike and get better wheels, you'll notice that before you will a drivetrain upgrade.
Getting something under $1000 new should be very easy, shouldn't even have to shop around much to find it. You're most likely limited to aluminum frames at that pricepoint but there are some decent steel offerings at those price points, like those offered by jamis.
Test riding is the best option, you should find out pretty quick what the difference between pricepoints are, assuming the bike shop did their job to make sure the bike is in god working order (not all do). Skipping gears and poor shifting from new components is not a bikes fault, it wasn't set up right if that's the case.
I think sram apex or rival are the best performance per dollar component groups but they often are saved for more expensive bikes builds, shimano 105 following closely behind. Many people who ride road "lightly" will be well served with tiagra and or sora, especially if you can get some of the older 8 or 9 speed setups (10 speed is much more expensive to maintain in terms of replacing chains and cassettes).
Campy is cool stuff too but it doesn't come stock on anything and it's pretty much always more expensive to build up a bike to get something already built. The lowest end campagnolo is still good stuff, they pretty much just don't have low end stuff, kind of like sram, though apex and rival are priced towards low end but function similar to the high end sram.
Used is a good option to start out, you can get better components for less money. There should be a lot of bikes going n sale as 2014 models should be on their way in soon. Consider cyclocross bikes as well, not just road. They're fairly similar and more versatile since they can take wider tires.