ok i have my zen cart installation up.

Do you guys recommend starting with adding a product catalog, or to first get a design?

I will have many products with many categories. What is the recommended way to organize a catalog? My guess is that i will do it offline then upload it. Is there a program that makes this sort of thing easier (perhaps some sort of catalog manager?)

Also is there anything i should keep in mind as far as SEO before i begin. i understand i will need to hire someone for SEO, but i want to make sure that there isnt something i need to be doing / keeping in mind before this point.

also is there a way to figure out out much certain keywords cost to advertise on with google. i just want to have some idea how much i will be spending on advertising before i launch. for something like "buy stereo equipment," what do you suppose google charges for the top ad -- a range or something would be fine.