Hey blue
I do believe that people can become demon-possessed, just like in the bible. It isn't terribly common, but it does happen. However, a lot of people will claim to have trouble with demons to make excuses for poor behavior, when it's actually their own sinful desires behind their actions.
Any spirit-filled believer can perform an exorcism, but it is important to make sure that the affected person actually wants the demons gone. And if the affected person doesn't become a spirit-filled believer, the demons can come back, in greater numbers.
I do have experience with the subject, and if you want to, you can PM me. I hope everything turns out all right.