Do you mind if I ask your age? I was a bit of a late bloomer too and from that experience I recommend not falling for the first girl who makes you feel good. Get out there and internet date until you have a feel for what you want.
The best way to overcome insecurity is to find someone who makes you feel safe, that type of person will allow you to be yourself and still feel loved. A little positive psychology helps too. Imagine women you date might be just as insecure as you on the date and that looking great or sounding smart aren't nearly as important as being a rock that makes her feel less nervous. Snuggle with people and animals as much as possible... Look in the mirror and try to love yourself.
You have to learn how to say "F it" (not out loud), because, for me, insecurity came from caring too much about leaving a perfect impression. I've found that if you care and worry too much what people think of you... then add a mental "F it", you won't go overboard, but instead balance out.
As for the girl, that's your call. It sounds like you'll have a ton of conflict, insecurity, and heartache dating her. But, it might be good to experience. Or you might just want to protect your emotions from that rollercoaster. It's a personality choice. I prefer to ride rollercoasters, but some don't.