Can this harm my PS2?
Not if you follow the instructions exactly how they are. Also you have a slim to no chance of breaking your PS2 unless you are completely illiterate. This is a very ease and simple modification to your ps2.
Can I get banned for having a mod disk?
Yes, you can if you have the mod disk in at the DNAS screen. But the instructions call for you to take the mod disk out and put in your original SOCOM CA disk way before the DNAS screen appears. So in other words you're safe.