First of all..yes you'll want a doctor before you have the baby. When you get to the hospital to deliver, they'll ask you who your baby's doctor is (the doctor will usually see them in the hospital unless they don't have privileges). You can also interview more than one doctor/practice (I did the 3 most recommended ones when I had my first child).
Things to ask: what is your emergency policy, can I call after hours, weekends, holidays, etc., what hospital do you use/recommend, will you see my child if they are in the hospital (trust me, if this happens, and I hope it doesn't, you want your doctor if they are capable). Ask what their views on immunizations and antibiotics are, see if they match your feelings or if you feel comfortable with the answer. Ask about their sick policy, can you call and get in the same days most of the time or is there a day or so wait (I would avoid that).
I have a group practice because they're open every day but Christmas Day. I love knowing I can see someone that has my son's chart and knows and trusts the doctors I've seen before, but I wanted to know that for most of the time would I see my doctor, or a different doctor every time (I wanted my doctor unless if was New Years Day, when we did go in and saw who was there).
I highly recommend Pediatric Associates on the Plaza or Leawood (maybe this is there other location). I love the practice, my newborn son was born with some problems so in the first month (he'll be 2 months on Feb. 10th) I think I met all the doctors at the Plaza office (nights, weekends, holidays) and really didn't find a single doctor I didn't like and my doctor followed up with us when he was back in the office.
Good luck and Congrats!!