100 miles is nothing - it's an hour and a half drive (at least in MI). John and I have been doing 100 miles for a little over 3years now. Just figure like this - if he's going to be working on the weekends, then you drive down on Friday after you get off of work (always helps if you can work through lunch and leave an hour earlier), and drive home later on sunday night (for me I usually leave his place around 7pm or so, that way i have time to chill and wind down for the night). If he's not working weekends, then you guys can alternate which weekends who drives. It was nice because John and I were in school when we first started doing this so we knew our schedules (with exams) way in advance so we could plan out 4 months at a time - we just sat down with our calanders and marked who was going where. This may or may not work as well for you if he doesn't have a set schedule, but you'll figure out how to make it work.
Oh I should also add - it's not always easy as it sounds. There are times (at least for me) when he would leave and i'd start

like a baby, or times when I would drive away from his place with tears in my eyes. It only usually lasted a few mins though cause once I got on the highway I had to focus on what I was doing, and know that I'd be seeing him in 5 days. Most times I was/am ok though and it's not that big of a deal, you get used to it, i promise

(doesn't make it necissarily easier though!)
Honestly, I'm going in the opposite direction of you guys and I'm freaked (a little).

We're going from 100 miles apart, never lived in the same town to moving in together in Utah. Can we say scary?