When the bank I was previously with hit that benchmark, finding resources on implementing or putting together your FIDICIA documentation became somewhat of a task. Our external auditors did not have any other institution over $500M, so together we came up with banks of similiar size and structure for which we had some contacts and visited with them. At least two of them shared their program and documentation format. However, if you are regulated by OCC, you should look to 12 CFR 363 for guidance on requirements.
Another item you will need to consider. Your audit committee has to be made up of members who meet certain criteria, which is determined by answering about 5 questions. Simply being outside directors may not be enough. Their status, in relation to the questions, should be reviewed annually and approved by the board. Again, see the CFR referenced above. In addition, we had our external auditors hold a "special meeting" to explain the new requirements to them and what their resonsibilites w/b in relation to that. They need to know that they are responsible for ensuring risk is adequately identified, disclosed and managed, and that they are in effect the auditors supervisor. Our department always met with them after the a/c meeting without any other officers or employees present for candid discussions or questions. The regulators really like that!
The examiners will want to see a strong program with detailed workpapers. I found the attestation and format, although a requirement, were not the main focus during the exam. They were more concerned with the audit program, my qualifications, resources (usage and adequacy), and my workpapers. That is where our E/A's were a huge help. We decided to mirror my w/p format after theirs, which also helped them at y/e to move through them quickly and use a lot of what I had already done. And, at least once or twice a year one of them would come review the w/p's, provide suggestions for improvement and/or bless the program, reports and recommendations. The system worked well and was "strongly" accepted by the examiners.