Chevy does sell SUV's in Argentina- not Yukons- the biggest one is probably the Blazer. You can probably get one that seats 6, but it will be physically smaller, both inside and out, than your Yukon.
http://www.chevrolet.com.ar/
But in Argentina, virtually no new cars are sold with big V8's, either gas or diesel. The Blazers here come with 2.4 liter turbo diesels.
So, while there will be GM experienced mechanics, it is doubtful there would be parts for your Yukon. Some parts would probably have to ordered from the USA- if you are diplomatic, they probably can get shipped in for you more reliably, and cheaper, than the balky argentine post office. But it still would be a lot more complicated than having repairs done on a car model that is sold in Argentina.
There are many models of minivans and SUV's available here that will seat 6, both new and used, but all will cost more than equivalent vehicles in the USA.
I have a friend with 3 kids, and he drives a Picasso-
http://en.wikipedia.org/wiki/Citroën_C4_Picasso
I have ridden in it a lot, and it is much larger inside than you would think.
Available in a 7 seater, these are similar in size to a Mazda minivan in the USA, with, usually, a 2 liter turbo diesel.
This size and shape of vehicle is a lot more practical in Argentina, where traffic is congested, streets are small, and parking is tight.
I suppose, if you live in a gated community, with off street parking, and you always pay for parking in lots or garages when you go out, the Yukon wouldnt be too bad, but it still would be harder and more work to drive thru the traffic in Argentina.