Poor Business Bookkeeping for small business, can I still save my business if i get everything squared away?

I started a small business with a friend of mine, 3 years ago. He was in charge of the bookkeeping, so i trusted everything would go smoothly. well he was filing our taxes and what not every year but he never used any of our receipts for supplies that we bought as a write off...we have a general Partnership and over the time he has become very lazy so he agreed to leave the business. I want to convert our General partnership to an LLC to start fresh and do it the right way instead of depending on someone to do it for me.. If i do that what would be the best steps to take for bookkeeping for my small business and for my tax write offs? Thanks so much. My only other option is to stop business all together and start fresh with a new business name and everything.