Start by breaking the word vegetarian down. Vegetarian usually means one who eats no meat, but eats eggs, dairy, and other animal products.
Vegetables and tofu? What part of this are you having trouble with understanding? I really don't get what you mean by this.
Seitan, beans, and I forget the 'chicken' substitute!
You won't know the difference!
Try some vegetables and don't eat anything with an eye (except a potato)
Does that mean jelly fish are ok?
There's an 'i' in fish.... :o)
There are many, many good books, and probably online sites that can get you going in the right direction. Start easy and do the nutritional research....
Your profile says you are 13-15 years old. A well balanced diet is very important when you are young and growing. I would get a physical and speak to my doctor before you accept this lifestyle. You are still growing and it is important you get good nutrition.
Good Luck to you and your mom.
Cut out any red meats to start with and replace chicken with Quorn (tastes and feels like chicken but isn't).
Any good supermart in the frozen section.