Check the Capers for activities. They have a singles meet and greet. Don't know if you'll meet that special someone on a cruise, but you should have no problem meeting people to hang out with.
I don't mind the inside cabins, I just had one and we saved alot of money, it was great. If you cruise single it is about the only way to go, as you are already paying 150% of the normal rate.
You can get your cabin assignment at least 10 days prior to boarding usually. Some people get them alot sooner, it depends on several factors. I have booked Riviera deck on a Guarantee, and have been upgraded 3 decks! It just depends on how early you book, and the demand for the sailing.
No worries! You are going on a cruise!