Owner serviceable batteries?

So I found this write up where a guy repaired his Camry Hybrid battery pack:
http://imgur.com/gallery/j8Bcp/" onclick="window.open(this.href);return false;

Is the Leaf's battery modular like this and owner serviceable? I imagine it'd be a challenge to remove the pack. Maybe replacing a bad cell instead of the entire pack? Or performing maintenance like this person did?

Yes, the Leaf battery pack is modular. But buying new cells is not yet feasible. You may be able to buy a salvaged battery pack but please don't do it on my recommendation.

Photo of the Nissan Leaf battery packs:
http://commons.wikimedia.org/wiki/File:Nissan_Leaf_012.JPG" onclick="window.open(this.href);return false;

I wonder if there are any disadvantages to having a mismatched pack, with, for example, some 2-year-old cells and some 6-year-old cells. Seems like when the oldest cell discharges, it will be hard to squeeze any energy out of the remaining cells because you won't want the weak cell to reverse polarity.

Bob