I have never bought any kind of precious metals, so please excuse my ignorance. I went to some of the sites recommended here to browse a bit, and see that coins that seem to be of the same exact weight and purity can have vastly different prices depending on condition and year. Does that kind of thing matter if you are only wanting to have some gold for emergency and aren't a collector per se? (For example, if I wish to use the gold or silver to trade for a necessity in some dystopian future,  will those things matter any more?) This is probably a dumb question, so I apologize in advance.

Just one opinion from an experienced metals buyer:
Stay away from the numismatics (i.e., collectibles), which will carry higher premiums for the same weight.
Stay away from "rounds" (i.e., slugs of metal minted by private companies), because they are less liquid (i.e., suspected by potential buyers of being fakes).
Go with Silver Eagles (American) or Silver Maples (Canadian) with a "BU" rating ("Brilliant Uncirculated").  
If you go to Apmex of Gainesville, this will be your cheapest option (and the most commonly purchased).  These are produced by the mints of their respective countries, and are widely recognized (and therefore less suspect of forgery, and therefore more liquid).
Alternately, buy "junk silver" (i.e., previously minted circulated 90% silver coins).  Pre-1965.  You need to do a little math to make transactions because of the 90% (vs 100%) thing, but nobody will deny their authenticity.

Coin shops will buy back gold coins but they'll lowball you a bit so they can get a discount.  Non-coin shop people will buy coins at spot price (i.e. current market price) + (maybe) a small markup.  A buddy of mine had a bunch of silver that he sold on craigslist so he could pay off school debt.  But I would not buy any metals unless you are willing/able to keep them long-term, just to avoid the hassel of trying to sell.  That's just me.

Alternately, buy "junk silver" (i.e., previously minted circulated 90% silver coins).  Pre-1965.  You need to do a little math to make transactions because of the 90% (vs 100%) thing, but nobody will deny their authenticity.

I should add:

I've heard many Trads talk about the "Pre 1955 Missale" which always confused me -- but they mean "1955". I could have the year off by 1 or 2 digits, but you get the idea.

In this case, 1964 and 1965 makes all the difference. You can find 1965 quarters and dimes in your change today, and they are worth nothing extra. But just one year earlier, and they are made of 90% silver and you want to hang onto them!

As an interesting side note, 50 cent pieces were 40% silver for a few years, from 1965 - 1969 I believe. So keep those as well.

The most valuable (or old) coins you can find in your change today are pennies and nickels. The current run of pennies began in 1957, and nickels changed to the current material/design in 1939. Of course, they recently changed the design, but the material is the same. So you could easily find nickels from the 40's and 50's in your change, and people aren't racing to remove them unless they like "old" coins.