Another point is puchased/downladed games or DLC may need to be declassified/deactivated in Settings to allow re-download use on another PS3. Multiple downloaded copies of same purchased game wont work across several PS3's. Most important is use Backup Utility or PS Plus backup before any HDD transfer.

I had the same problem with very tight screws on PS3 power supply. I solved it by purchasing a Screw removal / extractor gripping pliers long nose style , with unique non-slip jaws for quickly extracting damaged / stuck screws. ENGINEER PZ-60 Neji-Saurus,Silver. ( bought mine on Amazon)

These pliers have special grips on tapered end to hold and turn stripped or rusty screws. It took a lot of effort, but screws finally came out using these pliers. A bit of sewing machine oil and prising under the washers with a flat screwdrvers helps too. Failing that, take it to repair shop as they are VERY TIGHT screws on some models of PS3.