Install .CSV feeds into website

I have an existing OS-commerce website and i get my product from a company whose inventory count changes daily. They provided me with .CSV feeds to update my site regularly on product availability. I need someone to incorporate these inventory and product .CSV files (Excel format) into my website to work smoothly with existing data on site. I also have another companies feed that I want installed (though I dont have their products loaded yet). I need someone who KNOWS HOW to do this flawlessly. I do not want to create a new problem after loading these feeds. Knowledge and competence a MUST!