Sorry, credit goes to DBCstm for that tip. I’ve only done a few packs (some very easy and some very difficult releasing some magic smoke 
). It seems to me that one area to start prying up on the seam to pop it apart is nearest the power connectors (where it makes contact to power the laptop) and then hinge it up and over the other side (as Gj says). And also as Gj said, be sure to only cut one wire at a time! Easy mistake to make. Don’t get in too much of a rush; take your time.
As far as testing cells afterwards: There is a voltage limit where you keep cells above and toss cells below (voltage as-is out of the pack). I think that limit is about 2.5v??? Then you charge up the pulled cells, measure voltage off the charger, measure again 24 hours later, and then I measure 1 week later to make sure they are not self-discharging. I think someone told me that up to 0.10v is acceptable for used laptop pulls (???). Personally, all of my pulls have only dropped about 0.01v to 0.02v over the course of a week. (If you have a hobby charger, skip the following.) My next step is then to put them into a flashlight with a direct drive driver and compare tailcap current on high with a known good cell. Lastly, a runtime test in a light where you expect a certain runtime (i.e. a light with an XM-L and a Nanjg 2.8A driver should yield around 45mins or a little more if your cells are expected to be 2600mAh) - check tailcap current over that runtime though because you may find the light last for 58 mins but only pulls 1.5A or so (like my recent LG pulls).
-Garry