Welcome to the forum.
The only thing difficult about Clark County is that residents must register their handguns. Non-residents can be in Clark County for 60 days before this is necessary.
You do not need a permit to carry openly. You do need one to carry concealed. You can buy a firearm from your sister but if it is a handgun you will need to get it registered to you. I'm sure others from Clark County will be happy to fill you in with the details on that. I'm from Reno so I do not know all of the specifics.
Check out this pamphlet : http://opencarry.mywowbb.com/forum36/12253.html
It answers many of your questions about where one can carry and provides links to the actual wording of the law.
Walmart has a corporate policy that is to allow open carry if the state allows it. It is still possible you might be asked to leave Walmart and other stores. I have been asked to leave a few stores, but not Walmart. If asked to leave you must leave or you could be cited for trespassing.
You must have a Blood Alcohol level less than .08 to carry.
Nobody can legally take your gun from you if you are legally carrying. If an officer asks for your gun I would tell them that I do not consent to the seizure.
Nevada has preemption laws that are designed to make local laws void, however lately the attorney general seems to think they don't apply. I'm no expert on Clark County but the main thing that comes to mind is that North Las Vegas municipal code says no deadly weapons in vehicles.
I have been confronted by law enforcement a few times in Reno but they have never charged me with any crime. Be sure to have a good understanding of the law so that if an officer questions you can respond with confidence.
Definitely, you should look through the Nevada Revised statutes yourself and come to your own conclusions about the law. That is the best way to understand the law.
I don't know what the deal is in Utah but that sounds pretty severe. I know Utah basically says that without a permit a gun must be two actions from firing. That sounds pretty harsh.
I'm not a lawyer and nothing I said shall be construed as legal advice. There are many things to know about the law which I haven't covered in this post.
You can search through Nevada laws here: