Tools to find best-value options for public transportation and internet access in Munich

I'm off to Munich in a few days and I'll be staying for 3 days. I'd like to know what are the tools to find my best value options for airport-to-city, in-city and city-to-airport public transportation?

Also, I need to have access to the internet, most of the time. I checked available free wifi hotspots but as it seems, they're not enough for the amount of moving which I've planned. I'd like to purchase a limited time (3 days) data sim card, so you won't miss me here in the SE.

Are there such options available in Munich? And if yes, where can I purchase them? and what are the tools to find free wifi hotspots in Munich?