I first found the video on YouTube and it helped me through the disassembly, coming down to the end the video skipped over some minor but necessary steps though, so I came to this guide to be sure and to assist in the re-assembly.
I got a lot of trouble to fit the Blu-ray cable back into the motherboard, but a friend helped me out there. Instead of the heat gun I put the board in the oven at 200 degrees for 10 minutes as some recommended.
In the end the PS3 worked! But with all my troubles to get the Blu-ray cable back in I smudged the thermal paste on one of the chips a few times and noe it looks like my PS3 is overheating after a few minutes of use.
I'm going to get more thermal paste and redo this guide, but just to replace the thermal paste.