... it wasn't entirely clear what it all meant.

So I hope you'll excuse this intrusion from a regular AC flyer. Next Saturday Nov 13 (or maybe Sunday) I'll be flying SYD-PER in J. I found a great thread about people's preferences in J seating, but some apparently common knowledge has left me behind. So a few questions if I may:

1. Is a 73H actually a 737-800, "H" being the 8th letter of the alphabet?

2. Is there any way to tell in advance what type of 767 is flying that day -- i.e. 20, 25, or 30 J seats, or more importantly 2-2-2 or 1-2-2 seating?

3. What are the odd of getting row 1 middle seats (only 2 instead of 3) on an A300?

4. What is a Millenium seat, and why should I care?

Many thanks in advance.

(BTW, I'm currently on the 12:40 A332 flight, but I can take any flight that day, or Sunday.)