Experience with oscommerce is a must! The site you will be working on has been modified alot with outher contributions and custom work so you will need to know what you are doing - it's not as simple as just installing contributions.
The work will need to be completed asap. Please give a genuine estimate when bidding.
1) Make Admin fields longer - especially customer details.
2) Add quantity box on product information page - ideally below 'Add to cart' button.
3) Have a facility to bypass the payment section with your cart and request to collect the goods - They would need a box to put the collection details in. Also a "Shopping List" a list that they can print out and bring into the shop. And if possible a memory facility so that the goods could be sent in the end if required.
4) Install Seperate Pricing Per customer (or similar) so that traders can login and see different prices. We need to be able to apply the discount to all the products at once. There will be atleast 4 groups of customers, each group will have a different discount ie. 15%, 20%, 30% and 40%