Customize prestashop addon

Now let me make it clear, I'm a Php guru, I just have a lot of responsibilities to add this to it. So I have this prestashop addon (called DevisPerso) that I bought which I thought could meet my needs but was a little different than what I thought. So I need a little customization. The addon is a "request a quote" addon. This is because our website relies on bidding rather than the traditional 'add to cart' option. So what I want to achieve:-

1)replace all "add to cart" of items to "request a quote"
3)when user clicks on "request a quote" button, the item is added to his cart (shown on the right side of web page ... .will make picture available to winner of bid). now when the user clicks on "check out", a form will appear which the user will make a bid for the products
Details is sent to the back office for approval before he can proceed with buying.. you're not doing this from scratch, I'm sending over the file so you do this little customization to it. It's just a little tweak trust me very little. The addon accomplishes all this is just a little addition you're adding!

4) create a testimonials page which should work in the same way. Users submit their testimonial at front office -> appears at back office and admin approves it, then it appears of the front office testimonials page.