Welcome to the glory and madness that is Dwarf Fortress, and may your beard grow long and your booze stay flowing!
Turning on Cave-ins, Temperature, and Weather will increase the similarity to standard, unmodified DF, and while doing so might cost some bearded lives, you also won't have silliness such as dwarves swimming in magma. The standard pop cap is 200, iirc, but 150 is large enough to trigger all of the in-game events that require certain population levels.
I think you'd be surprised at how quickly one learns to read the standard ASCII, but any of the included tilesets will likely suit you fine. Personally, I started with Phoebus before shifting over to square ASCII, but I think Ironhand is another often-used tileset. Haven't used either for a few years, so I don't know if that still holds true.
The only things I may suggest for a beginner to turn
off are Aquifers, as it allows you much greater freedom to embark where you want, without worrying about having to get through layers of water-filled soil before you can hit stone. Some folks enjoy the challenge, but breaking through them gets a little old after the first few times. If you want to leave them on, I'd suggest checking the wiki (
http://dwarffortresswiki.org/index.php/DF2012:Aquifer) for tips on getting through them quickly and effectively!
Hope this helps (and hopefully someone will correct me if I'm horribly wrong on anything) and feel free to ask any more questions on the forums. Everyone's usually quite friendly!