Can't fault this guide.
* if you don't have a putty knife & you don't mind some scratches, a thin butter knife will do the trick for getting the case off.
*if you plan to replace hdd with an ssd - you may need to rejig some of the internal wires that run around the edges of the hdd/ssd: after I installed the ssd, and returned the wires to the tight track around the side and socket port end of the ssd, and turned the machine back on, there was a high pitch interference noises coming out the internal speaker every time the drive was active.
The solution: make sure the speaker wire isn't where it's *supposed* to be! There are three sets of wires, include the speaker pair. I reversed the positioning of these with respect to the SSD, i.e. I moved the speaker pair to be furthest away from the SSD, and *didn't* tuck them back in under the plastic lip beside the ssd connector port. I turned it back on, and no more high frequency whining whenever the drive is active