I started commuting 13 miles each way to work basically from nothing. This will definitely get you into better shape.

Just give yourself time to adjust and listen to your body. Going 0-100 miles a week will be hard on you. Not too hard, but I found that I had to ease off at times to keep minor irritations from becoming big problems. You can push through muscle soreness and generally feeling tired, but don't try to just toughen up and ignore things like tendonitis or saddle sores or else you'll be taking some serious time off.

The biggest thing I had to be wary of: personally I can't ride that many hours a week without bike shorts - not for padding, but to minimize irritation and for moisture control. Whatever solution you decide to go with, just keep those factors in mind.