1. As said above, this depends on where you land, (Tokyo? Osaka?, or maybe Fukuoka?)
2. How much money should I expect to spend while there for food and travel costs in USD?
This also depends on how you want to travel. Budget travel or?
3. Any places in Hiroshima you would recommend to visit?
What is your interest? For Jpn baseball, Hiroshima Carp has the most souvenir choice compared to other team, so visiting the Matsuda stadium where there is a big souvenir shop may be one interesting stop. There is always Peace Park. If you are female of buying something for your female friends, you can shop Kumano-fude, high quality brush for cosmetic made in Hiroshima. I believe there is a exclusive store that sells only Kumano-fude in shopping arcade near the Peace Park. Miyajima, is another choice.
But, 14 days in Hiroshima?! Unless you are visiting relative or family, 14 days in Hiroshima alone seems waste of opportunities.
4. Has anyone stayed at the Grand Prince Hotel Hiroshima before?
Location of the hotel is remote from the major shopping/restaurant/central area. However, there is a direct ferry(?) service to Miyajima, I heard.