First of all, congratulations on dealing with your fear of flying and being frank here about your fear. As for more specific matters...
Originally Posted by
beachmouse
Don't be afraid to ask questions at the airport or on the plane or say that, yeah, this is your first time flying. The default assumption from most employees is that any given passenger know the routine from walking into the airport to picking up any checked baggage afterwards and they'll treat you as such unless they know otherwise. If you're uncertain bout something, it's often easier and quicker to ask questions up front than to try to just kind of float your way through the process.
Of all the excellent pieces of advice you've already received in this thread, I'd say this one is among the best. For instance, it probably won't be obvious where the priority security lane is for first class travelers. Don't be shy about asking someone in an American Airlines uniform - from what you've said, I assume you're flying AA - where to find it. At the X-ray conveyor belt that your luggage passes through at security, you might ask the uniformed person by the belt what to do, explaining that this is your first flight. And once on the plane, you might mention to the FA and the person sitting next to you that this is your first flight, so please bear with you if you don't understand and have to ask about some basic stuff. Most (though sadly not all) people will be understanding and helpful under those circumstances.
Other bits of advice:
1. I'm your height and strongly prefer the non-bulkhead seats, for reasons others have stated: You actually have more legroom sitting in another row in first class. In addition, on many (but perhaps not all?) of the AA 738s the seat recline function is nicely set up so that it slides forward even as it tilts back, reducing the potential problem of the person in front of you tilting back very far.
2. In picking a row, be aware that for some planes it can be the case that the bulkhead row is actually row 2 or 3. As much as I fly AA, I can't recall, which row is the bulkhead in the 738. So if talking to a customer service representative (CSR) to reserve your seat, be clear on what seat you're selecting.
3. I agree that you're better off with an aisle seat.
4. Folks have mentioned that advantage of an exit row seat in economy, or of buying two of these. I'd still suggest going with first class because you'll find it (usually) a calmer environment with (obviously) a less crowded cabin and better service (including free drinks and a free meal), all of which should make your flight easier. In addition, while on the 738s the exit rows are indeed roomier than regular seats in economy, as in first class they are not so roomy that you won't have to get up to let the window seat passenger get by.
5. Great suggestion to distract yourself by at least bringing music and better yet a device into which you can download and play movies while in flight. In fact, you can keep an ipad or iphone out to watch movies even during take-offs and landings, though a laptop you'll have to put away during those periods.
6. At least for this first trip, I'd keep it simply by just flying between LA and DC rather than complicating matters with by starting in Fresno and dealing with the much smaller seats and cramped cabins on the plane from Fresno.
7. Assuming you've already bought your AA ticket, for future trips you might do some research on whether Jet Blue or Virgin Air might be better options for you (though be aware that they might fly out of other airports in the greater LA area, other than LAX), or on flying into JFK from LA on American, United or Delta if you can afford it. Jet Blue and I believe Virgin have larger first class seats for a few routes (though perhaps not into DC). The other three airlines have larger first class or business class seats between LA and JFK.
Finally, bear in mind that there are a fair number of people taller and/or heavier than you who fly regularly, so don't worry quite so much about being unusual in that regard. I realize your fear is more about the actual experience, but again you're taking the right steps to deal with that.
Have a great trip!