About your first question. I'm assuming your "getting tickets via Internet and then printing them at a 7/11" means the online lottery, which is only limited to TA members. So unless you're a member yourself, you have to get someone to help. Plus, you need a trustworthy friend who lives in Japan to help pay the ticket for you and have your ticket be delivered to his/her address. Otherwise, this option is more or less out for foreign fans.
And about tickets, if you buy it from the lottery, you won't be able to choose seats. They will randomly send you tickets. If you buy from a resale place, you get to choose from those available for sale. But then, you have to be prepared to pay if you want good seats.
As for seating plan, it really depends on how the tour stage will be like. Traditionally, it's with a front stage, but there's a high chance that the stage this time may be a centre one, like CDL. So we really can't tell until the show starts (since you're going for the very first show at Saitama, you'll just have to rely on luck).
But as a general guide, the floor seats will have the words アリーナ (arena) written on it, and the ones going up the sides are the スタンド (stand) seats, with 一階 and 二階 (1st and 2nd floor up) respectively.
There are generally no seating charts available, but you can Google each location's website, and they can give you a rough guide.
For example, for Saitama, the official website provides some "guidelines" for seating plans. May not be accurate, but it's the best reference there is.
If stage is in Front,
http://www.saitama-arena.co.jp/seats_info/arena_end02/
If stage is in Centre,
http://www.saitama-arena.co.jp/seats_info/arena_center/