1. My almost 2 week old loves his car seat. We have a Recaro Akuna (stroller) which comes with a Profi Plus (Infant carseat/stroller attachment). Your one should be fine, we introduced Cyrus to the seat in our room and let him sit in it for a few minutes when he was clean and well fed. You will probably want to plan a stop or 2 on your trip to give him a change and feed, depending on how often he needs to eat and stuff (with our schedule i would give him a good long feed before we left and then have a break half way through the trip).

2. Our seat isn't a fully reclined one (like a bassinet) as they only last until 3months old so not so worth while. Generally the slightly reclined/curved ones (that usually work as a rocker on the floor as well) generally seem to last until around 9months which is a little more worth it. Obviously don't let your baby sleep in the seat all day and night, but for a day trip or a car ride won't do any harm at all. As for sleep, as soon as the car (or stroller for that matter) starts moving, Cyrus is fast asleep and will stay that way until we stop.

3. We will be switching to a Recaro ProRide (hopefully, still need to arrange to get one into the country) which is rated for newborn to around 5years (after which we may still need to use a booster seat for a couple of years depending) once he grows out of the Profi Plus... if you weren't set on a specific brand like we are you would probably be able to get a seat that didn't suit a newborn but would last until older to switch to once you grow out of the first one.

I hope that helps. Basically make sure the seat you are looking at is suitable for your age range and hopefully will last for a decent amount of time. Also try to find one that has had some safety testing done.