Need modifications to sit-up
I have an old Mongoose Hilltopper with little mileage that I haven't used in years. I am starting to use it again. When I ride it I have to lean forward and lift my head which hurts my neck (age). Since I only want to ride for exercise and pleasure I would like to sit up. Should I buy different handlebars and a stem or would handlebars be sufficient? Is this a good option or is buying a different bike a better option? Thanks.