I have a workbook that I keep all of my customers updates on. Basically a list of part numbers and the quantities they want on each of the following days. When he sends over updates periodically I need to determine which parts are new and which I have. The problem is they come over with one part number per sheet (there's about 150 parts). I also need to update all my information with their new 'updated' information.

This question has a few parts:
1. Can I write a vlookup that bounces my cell value (part number) off of sheet names (the sheet names from their update-one for each part). For example if I have cells with part numbers 81069, 80873, and 80999 but my customer sends over an update with one sheet for each part number 81069 and a sheet for 80999 and a sheet for 91111. I want to be able to tell what parts I already have listed and what parts are new.

2. I have the sheet look at each of the part numbers on my list and return cells from the update from the sheet of the customers update with that part number. (I have a reference to =CustomersSheet.xlsx]81069'!$B2). I currently go in and physically switch the part numbers one by one each line, 81069 in the example will change to 80873. I have this part number listed to the left. Is there a formula that will switch the part number to a cell in that row? For example if part 81069's row has the formula =CustomersSheet.xlsx]81069'!$B2 and I drag it down to part number 80873's row, is there a formula that will reference/swap the 81069 with the new rows part 80873?. =CustomersSheet.xlsx]80873'!$B2

3. Lastly, my sheet has the part in column A1 then the values in column B1,C1,D1, ect. The customer has it transposed so the quantities are in row A1, A2, A3, ect. Is there a way to have it transpose these for the lookup or is it easier to transpose my sheet, do the lookups then convert back? I have other information/formatting it may mess up so I figured I would ask.

Here's a simplified version of what I am trying to work with.
Customer Example.xlsx

Sorry if this is not clear, please just ask if I need to be more clear about anything.