Customize a sign-up sheet plugin

I need to customize the sign-up sheets plugin [login to view URL] and wanted to find out what the cost would be to customize it. The link is to the free version but I have the pro version which I want to customize. The plugin allows volunteers to sign up for the preparation of different food items for the shelter dinner we host monthly for the homeless. Once the event is in the past, the sign-up sheets are no longer displayed. The pro version, which we purchased, has the capability to add categories and assign sign-up sheets to a category. I want to be able to post past sign-up sheets by calling the category even if the sign-up sheet is no longer active while at the same time keeping the capability of not displaying anything that is not active in the current sign-up sheets post. Here is an illustration: Category 1 is 2013 Category 2 is 2014. There is a page titled “Archived shelter dinners” which is the parent of several other pages, (“2013 shelter dinners”, “2014 shelter dinners”, etc.). I want all the sign-up sheets for the year/category 2013 to be displayed on the “2013 shelter dinners” page with the following short code [sign_up_sheet category_id=1], and sign-up sheets for year/category 2014 to be posted on the “2014 shelter dinners” page etc. I've gotten a quote for $100 from another company and I'm looking for something cheaper. Thank you