Not a pro, but to get you started...
That 2014 may well have the original battery pack, but I'm not sure how to confirm it. It's my recollection that 24 kWh LEAFs can only receive 24 kWh pack replacements.
While I am very happy with this 30 kWh LEAF, I learned that their capacity bar readings can be misleading depending on whether or not they have had a recent Battery Management System update. If a 30 kWh LEAF is missing bars, it is likely a genuine reading, but one that shows all bars may have had a recent BMS update and not yet re-adjusted. I got lucky, and this one still shows 12 like it did at purchase. It sounds like Nissan is replacing 30 kWh packs with 40 kWh packs--just something to keep in mind. I don't want to rely on the replacement warranty, though. I presume they can refuse it, for reasons such as missing an annual battery checkup.
I was originally looking for a 2016 SV but am really happy with with 2016 S I ended up with. I like the narrower, less-expensive tires, the seat fabric, the matte-black shifter surround (the gloss-black on the SV/SL scratches and scuffs easily, and shows fingerprints) and the simpler climate and audio controls with lack of touch screen (also stays fingerprint-free).
2016 LEAF S-30 w/QC "Lexie"