Good stuff! You'll certainly figure out what works for you. I love being car-free, but starting out car-lite is definitely a good way to ease into it. I save lots of money, and it keeps me in shape (so the longer trip times are more than made up for by not needing to spend gym time doing extra exercise). Here are some of my best tips:

-at first, sink some of your gas savings into the gear you need; you deserve to be comfortable and well-equipped. It makes the rides much nicer.
-don't over-do it... keep it fun. Also remember that when it looks awful out (rain, cold), getting started is often the hardest part. Once you're riding, it's still fun.
-Call to request a low-mileage discount on your car insurance?
-Set aside a box/space in your entryway for all your cycling-related gear (lock, helmet, beanie, gloves, keys). It makes leaving the house much more seamless if you have a 'bike only' collection box.
-I leave a couple pairs of shoes at work, and will sometimes try to take in a larger load of stuff on Mondays (clothing, snacks, lunches) so that I can skip bringing my bag a few days during the week.
-I recently bought a used kid trailer; it's super-useful for all my larger car-free errands. A trailer really expands your cargo options, and lets you practice being even less reliant on the car.

Keep us posted!