That soreness will go away in the next week or two, and won't ever come back unless you take an extended holiday from the bike (like a few months).

I think of every trip I take by bike almost as time travel... the trip takes 0 time, since if I didn't ride my bike, that's time I'd be spending on some other form of 'pointless' exercise (like sitting on the exercise bike in my basement).

Someday you'll ride up that whole hill, too! There will come a day when riding up is easier than getting off and walking up. Three days a week is a great plan; that's enough to build your fitness. I hope you stick with it and enjoy the health benefits. Maybe you should keep a few stats, just so that you'l be able to look back and appreciate how far you've come from where you are now (resting heart rate, weight, total mileage, average commute time, for example). Good luck!