Hey Flooooky and welcome to PokerStrategy.com.
That was very nice introduction and you found the right place to put your poker to higher level. First of all i would like to ask you if you have already chosen one of our partner rooms? Here you can find the list of them. You can also start you career with some free money. Free money is always good isn't it? 
Here are my answers to your questions.
What format would you suggest, cash or sit n go?
Just choose the one you prefer. I think it is easy as that :f_biggrin:.
Is it okay to start at NL5 cash?
I think you can start with NL5. But if you are a beginner i think starting with NL2 would be optimal. You can beat NL2 in notime and then move up step by step. I don't even think that it is mandatory to deposit 100 - 150. You can deposit something like 60 and go with NL2. Of course you can start also with NL5 and then move to NL2 if things go in wrong direction.
Is there any recommended reading that you guys can point me in the direction of?
If you decide to play cash game i would definitely recommend you to start and pass our Begginers Course. It is nice structured course with help of our experienced coaches. There are also Strategy Articles you don't want to miss. First you will have access only to Basic content but when you become Bronze or Silver you will unlock many more content as articles and videos.
Are there any books that are current? As all the recommended ones I have found are 3-4 years old.
Of course there are. You said that you are reading “the education of a modern poker player”. This is a good start. 3 or 4 years old books are a bit outdated. But still there are many good points. The most important thing is that you don't want to copy things written in books but you have to try to understand them.
Are there any sites I should be avoiding?
All our partner rooms are trustworthy. I would suggest you to go through forum and see the feedback of our users. Of course it is very important what do you expect form site. Do you expect many promotions, do you expect outstanding software, excellent support and so on. I think you cannot do any mistake deposit to one of our listed sites. Just follow the instructions correctly :f_cool:. I have accounts almost everywhere :f_biggrin:.
Is private coaching for me or should I wait until I have sufficient experience?
Private coaching is great. But i still think you can learn a lot without it at the beginning. It is pretty easy to become Silver member and then you can post your hands to evaluations and get response from our professional coaches. When you learn the basics and budget allow you to hire a coach this is a great option. I had a coaching consisted from 10 sessions and it was really great. I learnt so so much. You will receive all help needed here. Entire community is ready to help you on every step.
I would also suggest you to start your own blog to update your progress. Blogging is very popular among a lot of players. It is great also for motivation. In general just go step by step. With enough work and good will only sky is the limit :f_cool:.
I hope i answered your question. If you have more of them we will be happy to assist you. Good luck an your journey Flooooky and i hope to see you around.
Once you've tilted a few times, I recommend "The Mental Game of Poker" by Jared Tendler.. It goes without saying (so I'll say it) -- you should read all of the basic and Bronze strategy articles. (see comment on Beginner's course above)
