Money: Everything is credit-card, no need for cash. The only exception is for gas, they only take credit cards with signature (the USA uses Pin cards), so you just need to buy pre-loaded cards within the gas station. Iceland is QUITE expensive for everything (ie: cheapest thing at KFC is 15$). Make sure that you bring all the clothing you'll need.

WOW AIrlines: We thankfully had a decent experience with WOW airlines (4 hour delay), but they are notorious for lost baggage. We saw some other travelers who had their baggage delayed and since they were on a tight travel schedule, they had to buy new outfits in Reykjavik. I felt terrible for them -- a beanie alone was around 70-80$. Make sure to bring all your important stuff in your carry-on and wear all your jackets! As a budget airline, they had no food, blankets, or any entertainment.

Internet: Rent a WIFI-device (we used TRAWIRE). it's cheap and we were able to get the internet all over Iceland for all of our phones and laptops etc. No need for GPS since you can just use your phone. I also used Google Hangouts (download the Hangouts Dialer App) and was able to make calls through wifi. Very handy when our car broke down in the middle of nowhere...

Culturally: Icelandic people were generally very nice and they almost all speak English. I think the most fascinating thing I learned about their culture was that they believe in Elves! I read somewhere that the government wanted to build a road, but first had to hire someone who could speak to the Elves (in this case, a giant boulder blocking the intended road) and negotiate where the elves would like to be relocated (a location with scenic views and a couple of sheep). The government then paid to relocate the boulder! How wonderful :)