Excel Formula Project - Custom Quote

I need an excel expert to create me a custom formula workbook. The project is to create a "custom price quote" system for computer hardware related products. I want to create an excel workbook application. The purpose is to give my field sales reps the ability create custom price quotes for the customers. Dell is a good exxample of this. When you select a custom system, it allows you to switch out HW & SW parts (ie. harddrive, memory, operating system, ms office etc...). This will be the same thing except in excel, infopath or access. i would prefer excel since i have a little more knowledge in that than infopath or access. So basically worksheet 1 will compose of multiple questions such as "which harddrive do you want; how much ram do you need; what type of video card do you want" etc.. (of course these questions are only used as examples not actual questions). But the tricky part is, for what i am doing, they are all bundle packges of HW products. For example if they choose System A, it will consist of parts a, b, c, d, e. Or if they choose System B, it will compose of parts a, f, g, b, y and so on. Then after they chosen the system bundle, they also have the option of choosing other 'add-on' HW bundles, and so it goes down the list. At the end after the customer has chosen everything they want from the drop down list of bundle packages and add-ons, it will take them to the "invoice" worksheet where it will list the bundle packages and itemize every single part under the bundle, the price and qty. It will have a total at the end and i can add any discounts if applicable. I have the layout for the invoice worksheet, i just need the data to be inserted in there. I apologize if this description is very vaque, contact me for further details if you get a drift of what i need. Price for project is negiotiable, let me know what's a resonable price for a formula to do all this. I MUST see results before i send payment and it must work to my satisfaction. If there are errors, you are required to fix immediately. thanks!