An audience recording won't be a studio recording. You'll hear people talking, singing along, coughing, etc. You can't talk, either. You need to think of the recording as a souvenir, not a polished audio masterpiece.
But a S&G audience is probably going to be older and relatively respectful, and S&G are probably going to be pretty persnickety about sound. So depending on your neighbors in the arena, you might get surprisingly good results.
The post about "stack recording" means you should point the mics at the nearest speaker, not at the stage--your ears and eyes need different things.
With any modern digital recorder, the key is the quality of the mics. The recorder itself will do a superb reproduction of what goes into it. But the internal mics for the lower-priced recorders are likely to be geared for speech--a narrow frequency band--rather than music.
You can get very passable results with the Sound Professionals BMC-2 microphones, which are the size of pencil erasers.
Get them with clips, clip them on your (black for camouflage) shirt collar about as far apart as your ears, check the recording level on the opening act and give it a try. The BMC-2 are omnidirectional, like your ears, and if you clip them to your collar you can have one pointed left and one pointed right, also like your ears. It's not going to sound like "Parsley, Sage, Rosemary and Thyme" but you'll have a nice concert memory, assuming you don't have someone chattering away nearby.