Congratulations on your decision.
One thing I’ve oberseved here on BF is the sheer volume of information and opinions can sometimes be overwhelming for a new commuter. This seems to create a tendancy to “get it perfect” right out of the shute.
My advice –dig in with what you’ve got. In your shape, 12 miles one way won’t kill you no matter what your riding, wearing, etc. With the exception of safety (lighting,etc.) and a few tools, go slow with your purchases. Browse the information here but figure out what works for you. Tarwheels link is an excellent start.
I’ve been commuting for years and still find a great deal of valuable advice and tweaks here to make my ride more comfortable and enjoyable.