Software to automate file grabbing via ftp, detailed manipulation and uploading result

As a small business that retails on several online marketplaces (ebay, [login to view URL], .[login to view URL], .de etc) through one portal who sends modified csv, txt files to all these venues in the appropriate format for the items to arrive at that marketplace with the correct price and description etc. I have to manually create these files and upload them to this portal. I use excel saved as .txt files. I have to download the stocklist of warehouses via ftp, of which can be upto 10 million rows in length so I have to split them before even using them. This allows me to see what is still in stock and what is no longer in stock. I then download my active inventory from the portal and I have to then use Microsoft Access to compare the active inventory of my own to the inventory in the warehouses. I do this twice - once to find out what products have run out of stock and need to be removed from my inventory and once to find out what has come into stock that I do not have listed online - adds and deletes. Next I have to extract and format the information correctly to be uploaded to my online portal in the appropriate templates. Once the files are ready the deletes are manually uploaded. However I need to first filter the adds as I am not allowed to list specific content on sites like ebay so adult material and other similar items are removed by me searching the titles on excel for a selection of key words. Those items are then removed from the add list - this would need to be done also. The adds file is then manually uploaded. It is not a complicated process only boring and beyond my skill to automate - I do not even know the relevant skills to request for this project. Notes: I use ISBN numbers as keys for comparison Accuracy and a foolproof nature would be necessary as the result would ALWAYS need to be correct - any mistakes on sites like ebay can cost tens of thousands of pounds so this cannot make mistakes. Pricing etc has to always be accurate. Fluent English would be necessary due to my lack of knowledge on this subject and I would need to explain and show many parts of my business that are difficult to explain in broad terms Any questions beforehand please let me know and I will do my best to clear any problems up.