Modify ClerksCart Plugin for opencart - 48hrs hiring

Hello, we are building a multi-vendor marketplace for an online community that already exist. We are oriented on OpenCart with ClerksCart Plugin installed. Anyway we need two little modifies: 1) when a seller is going to list a new item, the space is fully customizable. We want that, instead of digit the full name of the item, the seller has only to select it in a dropdown select box (see pic attached). From admin panel we have to be able to add-remove-modify the items names list. Only us (the admins) have to be able to add-modify or remove names from the list. These attributes should be added to "Categories" too. 2) The option to add some mandatory attribute (ex: condition, etc): without complete these attributes the seller can't list new items. We (the admins) should be able to modify-add-remove these kind of attributes. The final products should be an OpenCart Plugin that we can easily install. That's all, feel free to contact us for any doubt or else, keep in mind that we already ask a quote to a local web agency. They could done this project in 7 days for 450€ + tax. Obviously if your quote is higher we prefer to hire someone in person. This is a long-run project, if we are satisfied with the result you can be sure that there'll be more work in the future. Thanks