How to Create Product with 100 Categories for a Blog Awards Entry Submission

I am using eCart 4.5.2 and I have PayPal Payments Pro, which requires I use PayPal Express Checkout and PayPal Payments Pro interfaces in my cart checkout page.

With that being said, how do I create and eCart product that will have around 100 categories. Buyers will be able to select up to 3 categories out of the 100 if they pay the basic price. If they pay an additional amount they get to select up to 6 categories.

The product is a Blog Awards Entry modeled after the Webby Awards. The buyer would essentially select categories for their Blog to enter the Awards and pay for their entry from my website, etc.

I am not sure how to achieve this but I am wondering two things:

1. Do I need to create a Entry Form with all the categories and functionality I need described in paragraph 2 FIRST and have this data somehow (I have no clue) passed on to the eCart checkout form? And then the buyer can continue to make their purchase using PayPal Pro / Express Checkout with their entries categories already embedded in the checkout form? If so, is there any example on how to do this anywhere?

or

2. Do I need to create an eCart Product with all 100 categories and options the way I need them as described in paragraph 2? If that is the case is there a sample of this or information / tutorials available that can demonstrate this?

Please advise at your earliest convenience.

I did do a search on "categories" and read several pages of material but none seemed to apply exactly to what I needed for my Blog Awards Entry deal.

Thanks very much for reading and reviewing my question.

Dante