CONGRATULATIONS and WELCOME!!!
You'll find lots of great information and wonderful people here!
In response to your questions - First, don't worry - I think we all have shared in both your initial excitement of wanting to have a DW and then the overwhelming feeling of where to start!!! But - you're right, this forum becomes part of your routine and you'll love the fact you can find answers to just about anything here!
I'm not using a TA - but that's because our wedding is going to be so small - around 30 to 40 people. Also, we didn't want to do an all-inclusive resort, but preferred a smaller boutique hotel. I contacted the hotel directly - we're getting married in Cabo - and I was told that it is customary for the hotel to offer a 10 to 15% discount if you book 10 rooms. However, since our wedding is in high season (at the beginning of Spring Break), we weren't eligible for that discount, but the owner was willing to comp the bridal suite for us. So - if you're not using a TA, I would narrow it down to 2 or 3 locations and contact them directly to get a rough idea. We love the hotel we're at because of its character and it is very reasonably priced. That being said, we also have friends that are making a vacation out of the trip and are renting private villas, staying at resorts, etc. There really is a lot of flexibility - just choose what you feel most comfortable with!
As for airfare - both we got discount codes from American and Frontier airlines - you can do that on their websites. They both say that there is a "minimum" number of guests that must book, however, customer reps from both airlines said that they aren't going to revoke the discount if those aren't met!
I got engaged at the end of August and we're getting married on March 8, 2008 - so not much time in between! We called and let everyone know right after we got engaged - and then we sent out STD's and set up a website immediately. Again, since ours is so small, we're in contact with all the guests pretty regularly!
Good luck - and I promise - things do calm down! In the beginning I was talking by email with my WC a zillion times a day - but now we just check in with each other about once a week!