Hey!
It can be SO confusing in the beginning. You've decided that you want to change your life, and that is awesome! Take a look at the "Diet Central" area. You'll find a list of various plans people are following and be able to check out the benefits & perks of each plan.
Here is a link to the area:
http://www.3fatchicks.com/forum/forumdisplay.php?f=102
You may see right off the bat that one or two plans don't fit your lifestyle, but may find a couple that do. Just select one that feels right (or that you find might be interesting to try!). It may involve a couple of different plans in the beginning to find one that you like. (This happens to many people.) You may even end up forming something of your own plan. Plenty of people do this here too!
About making mistakes. If you take some time to read what people are posting here, you'll find that half of it is about "mistakes". We are not perfect! No one here has done everything right 100% of the time. You know what they are doing though? Not giving up. Sure they may have eaten a few things that weren't the wisest choices, but instead of saying "oh forget it then" they got up the next morning and began anew.
Will you make mistakes? Probably. Will you give up when they happen? Not if you decide right now that this is forever, and therefore there is no quitting, even when they happen.
You CAN do this. Feel free to ask questions if you're curious about something. We're all here to help eachother out & give support. Don't be shy to use this site as a resource
Best of success!!!