Running Injuires

Hello all, I have just started doing triathlons. I am loving the sport very much and would like to train harder for next year to get a good time. unfortunately, my run is extermely weak (10:30min miles). I cannot train much because i get injured or feel pain very easily. It is never too painful that i cannot run (but people have told me not to run too much to prevent making it worse). So basically i have gotten shin splints, i stopped running for about 1 month and slowly got back to it once a week then twice a week doing about 2-3 miles nothing crazy on speed. So they got better but now i have plantar fascitis (the back of my feet hurt pretty bad after running). I have gone to fleet feet and what kind of worries me, is that the women there was a bit puzzled with me. I don't think i look uncordinated or anything but i think i have some supination issues. They bascially sold me a netural shoe and said that is all they can do. I have been told by others that orthodics are only for people with no arches, and i do have an arch. Any one have experience with this stuff? I would love to get to the point of running a good 2-3 hrs a week but that is just impossible now.

Thank you so much!

CORY