>>830272First of all, take cash with you. You can use us dollars everywhere in argentina. You need to apply for a permit and you need to do it by yourself right there in Mendoza, and it takes around 3 or 4 days for them to give it to you because their burocracy is meme tier and because they want you to spend money in the city. Don't do that. Use all the time you have to do easy day hikes and acclimate.
Bring all the gear your need with you, all of it because the stores in argentina are a fucking joke. The only thing you'll need to buy there is the fuel for your stove.
Keep in mind that the average argentinian will try to rob you at any given chance, so don't get your hopes so high and stay focused on the mountain.