Zen-Cart UPS Shipping Tools - Additional Modifications

We have a Zen-Cart site where UPS Online Tools have been integrated. We need to make some modifications to the UPS Online Tools to address a couple of issues the client is experiencing. Here is a description of the issue from the client. "The time in transit module is not returning correct options. If you try something outside of three day Ground transit times, it is not showing 3Day Select, but only 2nd Day Air. Example; I tried to select a valid Littleton, CO address with a ship date of Nov. 29th. This is three days by Ground, so it should return shipping options of Ground, 3Day Select, 2nd Day Air, Next Day, etc. All of the options ticked in the UPS module from the Admin side. It is only showing Next Day Air options. Also, I tried a valid Chicago address. It should show all options again, but is only returning 3Day Select and Next Day options. Tried a valid Texas address, that was four days transit time, so it should allow 3Day, 2nd Day, Next Day options; it is only showing Next Day options. If you click on “Checkout” from the shipping option select page to change your shipping date, change the shipping date, all of the Next Day options are gone; it is showing no shipping options, and does not allow you to move past this page. You are essentially hung up and can only change your address or just dump the whole session." "I figured out the transit time thing. I had to up the “Maximum Days In Transit” in the UPS module from the admin side to 6. It was 4. 4 made sense, 6 does not. It is still not returning the correct shipping options if you go back to “Checkout” and change your ship date; it only returns Next Day options." All previous modifications need to remain working when these changes are made. Previous modifications may be viewed in these project descriptions (http://www.freelancer.com/projects/PHP-Zen-Cart/Zen-Cart-UPS-Online-Tools.html, http://www.freelancer.com/projects/PHP-XML/Zen-Cart-UPS-Shipping-Module.html, and http://www.freelancer.com/projects/PHP-XML/Zen-Cart-UPS-Shipping-Tools.html) Module needs to be compliant with Zen-Cart development norms and allow for future Zen-Cart software updates without major issues (i.e. no modifications to core code where file override system is available. All core files modified must be listed and properly documented.) Please reply with examples of previous Zen-Cart work, UPS Online Tools experience, listing of qualifications, references, quote of time to complete project, and quote of price for this project.