Laptop Battery Rebuild

Hello, I have acquired a HP 6830S business laptop that died from the cheap Hitachi HDD crashing. I've ordered another drive, Western Digital Scorpio Black 250GB, to put back in it.

Now here's my problem:

Laptop batteries are expensive, but all they are is a case, a control board, and a set of LI-ION cells. I was just going to replace the cells and get on with using my new toy(I have been playing Minecraft using Ubuntu on an external HDD with the charger connected at all times). The cells have SE US18650GR on one line, and T G51170G29S on the other inscribed on the case. These show up as Sony cells, which is not bad, but the cells are still dead. The pack itself is a HSTNN-OB62.
What I need is comments on what brand of cells to order, and how big a cell I can put in it (what's the biggest 18650 cell I can get my hands on). Some other details that would help is what will I have to do to reset the battery circuit board to show correct charge levels, and do I need some of those cells with circuit breakers in them.

A little off topic, but what do you think about Windows XP(Vista, which came with the laptop, sucks   , 7 is too expensive, and 8 sucks) and Ubuntu dual boot? Also, it has 4 GB ram and core2 duo @ 2.4 GHZ, should I upgrade these components?

Thanks in advance for replies!