If you need "reliable" information about what you will need to apply for citizenship just go the the juzgada federal closest to your domicile and ask for a list of the documents that you need to provide to apply for citizenship. Apparently it can vary slightly from one jurisdiction to another. I needed only my DNI, a photocopy of my birth certificate, a certificado de domicilio that was less than 48 hours old, and "proof" of my means of living (income).
If your question is about the two year residency requirement I can tell you that the important date is that of your first entry into Argentina, even if it was before you received residency. That is the date that starts the clock on your "residency" in Argentina as far as citizenship is concerned. It shouldn't matter if you left the country since that date, even if you were out of the country for months at a time, especially if you renewed your DNI annually, but that might not matter, either.
When I applied early this year I asked if they needed my passport or anything from migraciones showing how long I had been in Argentina. I was told that they did not because I had the DNI. The secretary who took my application looked for the date of my "entro al pias" in my DNI as she filled out the form for me. You can read about my experience with the process in the thread: Argentine Citizenship for Foreigners: Can it really be this easy?
If I understand correctly, if you have a DNI you don't need a lawyer and lawyers may actually be prohibited from representing foreigners with a DNI who apply for citizenship. If you just go to the office of the court you should have the answer to your question in a few minutes. You only need to find a lawyer if they tell you that you need one. No matter what a lawyer might tell you, its the judge who has the power. A good lawyer may be able to affect a judge's opinion, but only if he is allowed in the court in the first place.