Is OCD a minor mental illness?

It depends completely on how severe OCD is in the individual.

My OCD is so mild the most I do is touch certain items like switches or banisters when I'm stressed. My ex has no mental health problems now but a few years ago he developed OCD so bad his hands were constantly infected due to over-washing so much they'd split and he couldn't leave work unless someone opened a door for him. To go one step further again a friends mother has OCD so severe she goes missing at night, she turns up crying and freezing in the street in the middle of the street: she can't go home until she's touched every single thing in the street.

When OCD is severe it can be life-threatening, behaviour takes over and can puts people in dangerous situations.

It all really depends how severe the OCD is, if it is affecting your daily life to the point of where it is limiting you in any way, the yes. But keep in mind it is completely normal for everyone to have a bit of OCD in them. :)

Yes, it is mental illness and can be very serious depending on the person.

I wouldn't say so, depends on the severity.

yes. you can overcome it.