There are two documentation for the two different NextGen gallery integration options. They both link to each other and is accessible to anyone before purchase:
2. http://www.tipsandtricks-hq.com/ecommerce/nextgen-gallery-alternate-integration-method-805
As a matter of fact all of our documentations are accessible to anyone before purchase. If you spent some time reading these documentation you will see that it goes over the pros and cons of both the integration options so you can decide which one suits you.