Congratulations! Commuting by bike is, by far, the coolest thing I have done in my life as a worker.

You will work out all the kinks you described. Leave some clothes at work. Get a set of panniers and pack them the night before. Pull out Google Maps and find a route that uses neighborhood streets, the alleyways behind stores, etc. I remember when the types of problems you are describing seemed insurmountable to me. Within the first few commutes, they were all resolved.

Good luck, and don't be afraid to ask specific questions of other commuters on this forum. People love to help.