I needed to see how the USB plug was aligned on the motherboard and your guide showed me exactly this. Since I am not able to solder I will ask someone else to do the job, but at least I know I tried my best. Thank you.
if you are referring to the hexagonal screws in step 2: yes, they are the worst! I had to drill one of those to push it so that it broke the small plastic base on which it stood. Of course you can't do it to all the 4 screws or you will have a non stable base!
if you are referring to the valve in step 3 - yellow circle - you can remove it with a flat screwdriver but it's not necessary if you don't need to replace that specific valve.
Hi, I think you can empty the boiler (the one depicted in step 6) before disassemblying the coffee machine. Just try to remove the water container (the one on the back of the machine) and try to "make a coffee". The machine should try to empty the residual water in the tubes, but probably some water will remain inside the boiler.
Either way you can open the boiler (step 6) on a sink so that the residual water won't wet your working space.
To remove the motherboard you need to unscrew two black screws with a 5 point screwdriver. I almost bent the metal cover of the motherboard before noticing that.