Since back/neck pain is a big concern for you, I do hope the bike you get will not have the seat be much higher than the handlebars. Bikes can only have seat and bar heights be adjustable to a certain extent but no more. Be sure to check on that.
Be sure to ask them if your bike can take at least 28mm wide tires if you want to ride on gravel roads...and ask them to put Kevlar lined tires on it before you go home with it. You will get way less flats on gravel with Kevlar tires.
By the way- most bike shop guys discourage them though, saying they will "slow you down". That's certainly true if you are racing. But they only weigh a tiny bit more than regular tires and they will save you from getting frequent flats when you ride those gravel roads.

Remember also that bike shops are usually willing to swap parts and tires for you when you are actually buying the bike and only charge you the difference in price of the part. Once you've taken the bike home however, they will naturally then charge you the whole price of the part plus labor when you want to change something like tires or gears or saddle, etc. Also you'll then be stuck with your "used" part.