I went to Argentina in 2008 (or 2009, can't remember which). Never felt unsafe or worried about kidnapping or anything like that (then again, I did not carry any but the smallest cash on me because it wasn't necessary). Spent two weeks mostly in the northeast part of the country using Salta (beautiful colonial city) as the base, in addition to a few days spent in Buenos Aires and Iguazu Falls on the Argentinian/Brazilian border. One thing to keep in mind is that Argentina is HUGE and has different climates when you move from one region to another, so you have to be really in tune with distances, varied climates, and varied geographies.
I would highly suggest hitting the library, bookstore, or Amazon and getting a Footprint Guide (or any others you can find - I used Footprint for my planning) as your first step. Only you know what you'd be interested in (I wanted to drive through the high Andes and see smaller indigenous towns, as well as a few large cities like BA and Salta, and Iguazu Falls). Argentina has just about everything. It is absolutely gorgeous. But do the research, especially on Pantagonia which is a severe climate and you need to be prepared in terms of clothing and expectations (and that depends what time of year you're going too).
I rented a car (in Salta) and drove with two friends around the Valles Calchaquíes, and it was one of the best road trips of my life. I had to take 2 internal flights (one to Salta from BA, and another from BA to Iguazu Falls) which were quite expensive due to national carrier monopoly (this is loosening though and I believe that more carriers are either beginning to enter the market or will do so in the near future). As far as money goes, I believe that the dual currency situation is gone (there used to be one "official" currency and another "black market" currency, but I think that's long gone). When I went, I did not bring dollars, use a money exchange of any kind - I just got money out of an ATM like anywhere else. You'll need to do some research as to best strategy right now because the economic situation in Argentina has really changed (luckily for the better since their colossal crash in the 2000s which was really devastating). It's an amazing country, very affordable, and you'll get high quality food and wine. I loved the northwest parts of Argentina that I was able to see and would gladly return.
