I think it would be easier to drive the car into the garage and enter the home through a door between the garage and the area where there is a fireplace (back of the house, behind the garage).
Not if the garage was used for storage. A lot of people don't use their garage to park their car. When police got to the house, his vehicle was in the driveway and not parked in the garage. I'm just assuming here, though...
I do remember seeing a picture of the garage open and crime scene there and it looked like there was a lot of stuff in the garage. I'll have to see if I can find the pic again.
If the garage couldn't be pulled into, that side door would definitely be an alternative since it was between the two houses and on the garage side of the house next door and there might not have been windows from the other house facing his house. No one would have seen a thing.
Edited to add: I found the pics and while I can see garbage cans, can't really tell if garage was full or not...sorry...
http://photos.denverpost.com/2012/1...rrested-in-connection-of-jessica-ridgeway/#24