WordPress Donation Plug-in / Add-on

I require a competent WordPress and Woocommerce coder to sort out a donation add-on which we cannot get to work. The support from the actual seller of the add-on has not been good.

The add-on is a donation type plug-in which is only supposed to show at check out, however it shows as an item and further more when you get to the checkout and add an amount, the calculation doesn't work and also when you try and reset it the amount stays as that previously entered.

The basics are:
Install the add-on
Ensure it doesn't show as an item
Ensure that the functionality works as it should so when you check out you have the options to make a donation which is automatically added to your basket

I want to start this on Sunday evening so please post your bids and ask me any questions as required.

Please check out my feedback as an employer. Thanks guys