Google "ada checklist for existing facilities" You will get several checklists covering everything.
Priority 1 approaches and access Priority 2 access to goods and services Priority 3 toilet room Priority 4 - water fountains, public phones, fire alarms all with word doc's
Other than ATMs, most of what it takes to assure that both sides of the service area (reasonable accommodation for employees and barrier free access for customers) is no different than for any other business with offices open to the public. Rocky's suggestion is a good solution. You might also contact your state bankers' association (if your bank is a member) & see if they can provide or suggest anything.