I think you should go for it! I worked as a receptionist in a law firm when I was 20. First, you should make sure you can type a decent amount of words per minute. Also, make sure you understand the programs in Microsoft Office 2007(most office jobs require you understand these programs). There are free online tutorials if you go to the Microsoft Office website. You can also download a free copy of Microsoft office and have access for 90 days. At the end of 90 days, you don't have to buy it: office.microsoft.com/en-us/?CTT=97
When you compose your cover letter and resume for a receptionist job, make sure you put down all of the experience you've had that might transfer: answering phones, computer work, the computer programs you know, interacting with customers, having a friendly attitude, being a people person and team player.
Make sure you wear a nice, contemporary skirt or pant suit to your interview. Buy something that is fashionable, but simple(no ugly old fashioned, outdated things and nothing over the top). Make sure you hair is perfectly styled and your makeup is nicely done but not flashy. Receptionists make the first impression of the company on all clients that walk through the door. They always need to look their best.
My best advice to you is don't give up! It might be hard to find a receptionist job with the way the economy is, but you're young and you have time. I hope this helps! Best of luck in your job search! Also, I see you're having problems getting back into school. I don't know what they are, but you could always eventually try a community college(you will take a placement test and everyone is allowed to attend regardless of their high school grades) and take part-time classes. You can even take them one a time in the morning, afternoon or evening depending on your schedule. Again, you have plenty of time. Just making a suggestion. :)