Fix errors in OsCommerce Site

We recently paid a GAF freelancer to create a module for OsCommerce that allows the shop owner to sell 'made to measure' blinds on the site. The module was created and allows the shop owner to enter prices according to size from within the admin control panel. For eg: Price Set 1 50(h) x 60(w) = £50.95 60(h) x 60(w) = £55.00 etc. etc. Price Set 2 50(h) x 60(w) = £70.95 60(h) x 60(w) = £75.00 etc. etc. Then when adding a product the shop owner can decide if it is a standalone product with a static price or whether it uses one of the predefined Price Sets. If the shop owner selects that for example 'Golden Oak Blinds' should user Price Set 1 then he sets this and a customer must enter the size in H and W that he requires and press the 'calculate' button to get the price before adding it to the basket. The current error in coding was not found during testing and has only just become apparent after customers have been complaining that they cannot buy the same product more than once with different sizes. This is because OsCommerce is not built to allow a person to add the same product (with different prices) more than once, instead it cancels out the previous entry and overwrites it with the last addition! (hope I'm not confusing you?!...please feel free to ask questions if you do not understand). This needs to be fixed URGENTLY as the previous freelancer we used keeps making excuses and has not done anything for 2 months!!...it has now got to a very embarassing stage with our customer so WE NEED SOMEONE QUICK AND RELIABLE! The other error is that when you view some of the products, the height and width fields that the customer needs to enter information into are pre-filled with data instead of being blank...this must be some sort of mySQL error and this needs to be resolved. The final error is that some products entered with images show thumbnails and when you click to enlarge the pop up screen in blank!!...I'm not sure why this is hapenning as it doesn't happen for all products just a select few. If you bid for this project please understand that you must complete these fixes within approx 1 week (give or take a few days). We have downloaded the HSBC payment module as the shop owner wants to use HSBC to take payments so we would like you to finish configuring this module too just to make sure that the whole site is working and that we do not make any changes that screw up your work!!....I don't expect you to charge us for the HSBC module as we have already installed it (and it's free)...but just want to make sure you complete the configs so that you can be sure we do not break anything after you have finished. If the above is not clear then ASK questions as we dont; want to fall into the trap of the last GAF freelancer where he claimed we did not provide enough info and that his wrk was completed according to the info we gave him!!...we expect you to be flexible and fix issues that we find with a professional and understanding approach!...not everything can be provided in writing - we are human beings and expect you to allow for a small percentage of communication error. Oh - and one final thing (sorry0 - the shop owner does not want 'new products' to be displayed within the category pages (only the front page)....this is a very simple change and you may aswell do it whilst you're working on the site for the same reason we provided above.