Addons, modules and overhauls?

Hey, I am building my own zencart for the first time and have some questions.

1. How can I "stock by attribute"? List quantity by size?

2. How can I have more than 1 image per listing? In my opinion, multiple stock photos should be default.

3. What are some alternate payment modules I can add? Alertpay and Google checkout are options I had in mind, but if I could accept checks or whatever that would be great too.

4. Are there any overhauls that would make the experience with the control panel a little more efficient and user friendly? The control panel is powerful, but like this forum I think they went overboard on the volume of options that could have been combined into sub-foldiers.....its too spread out and requires too many steps sometimes. I think it could have been done so as to be more time efficient for the admin without sacrificing options, though I do like that its powerful and that the options exist.

No need to re-ask your questions again since you have asked most of these separately.