Buying prestashop customization

I use prestashop to power a mobile apps store. Most of the apps/games are free and I get 20 downloads/checkouts everyday.

I would like to customize my store so that -

1. The free apps/games are downloadable after the user fills a cpalead survey. The experience here has to be really smooth and hasslefree for user. The survey itself must be integrated well within the site so it does not seem like we are pushing the user to another site.

2. The apps/games which cost money can be purchased by the user using trialpay. So instead of paying real cash to the app store, they subscribe/tryout/buy something else that trialpay offers. The customization here should be such that the option to get the game for free should be highlighted along with the game in the store front page. Trialpay offers graphics/templates that make this easy. The option to use this method of payment should be visible to the store during the checkout process.

The user flow is
1. Free game -> checkout -> taken to download page -> prompt to fill cpalead survey -> download starts after filling in survey
2. Paid game -> advertise that you can get it for free as an option -> checkout -> customer can choose trialpay option -> finish trialpay offer -> taken to download page

The ideal person will have experience with prestashop, cpalead and trialpay integration.
There is also the opportunity to have ongoing work as webmaster of the site.