I have found that as much as you might train in the gym for a particular non-gym activity (basketball, swimming, cycling, etc.), there is nothing that is truly equivalent to doing the activity than the activity itself. That being said, your training in the gym may not fully prepare you for the hill climbing that you will encounter on the ride home (although watching movies from the couch may be sufficient training for the downhill commute!!! LOL) and there is no shame in getting off your bike and walking it because after a while, you will be able to do it, not just do it but you'll wonder what all the fuss was about.

Yes to lights, racks, panniers (I hate backpacks while riding), fenders and a bike that makes you wake up and feel excited about riding. Did anyone mention a helmet? I would also like to recommend cycling shoes, even if you don't use clipless pedals, because the sole is stiffer than regular shoes which makes for better pedaling. Mountain style is good because they are walkable but there are some skate style ones and Keen makes cycling sandals.