well after further inspection, the screws that i tightened after applying the thermal paste appear to not be over tightened (i loosely tightened them with my hand,and gave a quarter turn with the driver after), as for the thermal compound,it's hard to say weather or not it is sufficiently transferring the heat to the heat sinks. (from visual perspective it looks to be).
After I formatted the old 60gb hdd out of another former ps3, and still ran into the HDD is not accessible error, I decided to give it a go using my current hdd out of my working ps3 (after backing up game saves, photos, etc) and after i ran the format utility on the PS3 that keeps shutting down (it said it completed 100%) and accessed the HDD fine during the format. after, however, while trying to again rebuild the database, I get "HDD is not accessible" error, along with the continued "update loading" screen when I try to load from usb.
Something else I found weird,was after the format of the working PS3 HDD was successful, yet accessing the drive kept failing, I decided at the end of the night,to transfer it back to my working system,restore my backups, etc, and save it for today.
Upon restarting my working model, I noticed all user data,game saves, music, and so on, to still be on the drive intact (and not formatted) contrary to how it appeared on the other PS3.
Any ideas on how (or where) the PS3 restores the O/S to a blank/new/etc HDD? (I'm wondering if that is damaged somehow,either from heat,Hardware or software failure.)
At this point I still would like to rebuild the system to it's former glory, however It's seemingly impossible, as I've ran into multiple (unrelated?) problems.
Thank you again for your help.