Hi there, my name is XXXXX XXXXX I'm a business law attorney with experience in all aspects of business law. I'll do my best to assist you.
1. If you are registering a public accountancy firm, you may register as a Professional Services Limited Liability Company. You would have to register an new PLLC
with appropriate agencies, transfer any assets from the previous LLC, and report accordingly. You can read more about NY PLLC law here: http://codes.lp.findlaw.com/nycode/LLC/13/1302
2. For an LLC that generates income, there is an annual filing form and fee. The fee varies depending on the income level. You can find more information here: http://www.tax.ny.gov/pit/efile/annual_filing_fee.htm
3. If you're starting a public accountancy firm, you must register as such. You may read more here: http://www.op.nysed.gov/prof/cpa/cpaptrshp.htm . This is a very informative link, and would likely provide you with much of the information you require.
I hope this answer has been helpful. I'd be happy to further clarify my response and follow up with any other questions. If you're satisfied with my answer, remember to hit the "accept" button. Bonuses and positive feedback are always appreciated! -Michael